Catalyst for polyester production, process for producing polyester using the catalyst, polyester obtained by the process, and uses of the polyester

ABSTRACT

The present invention provides a catalyst for polyester production capable of producing a polyester with high catalytic activity, a process for producing a polyester using the catalyst and a polyester produced thereby. The catalyst comprises a solid titanium compound obtained by dehydro-drying a hydrolyzate obtained by hydrolysis of a titanium halide and which has a molar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than 4. In the process, the polyester is obtained by polycondensing an aromatic dicarboxylic acid, or an ester-forming derivative thereof, and an aliphatic diol, or ester-forming derivative thereof, in the presence of the catalyst. The resulting polyester has excellent transparency and tint, a titanium content of 1 to 100 ppm, a magnesium content of 1 to 200 ppm and a magnesium to titanium weight ratio of not less than 0.01.

This application is a divisional of application Ser. No. 09/470,664,filed Dec. 22, 1999, now U.S. Pat. No. 6,346, 070.

FIELD OF THE INVENTION

The present invention relates to a catalyst for polyester production, aprocess for producing a polyester using the catalyst, a polyesterobtained by the process and uses of the polyester.

BACKGROUND OF THE INVENTION

Because of their excellent mechanical strength, heat resistance,transparency and gas barrier properties, polyesters such as polyethyleneterephthalate are favorably used as not only materials of containers ofvarious beverages such as juice, soft drinks and carbonated beveragesbut also materials of films, sheets and fibers.

The polyesters can be generally produced using, as starting materials,dicarboxylic acids such as aromatic dicarboxylic acids and diols such asaliphatic diols. In more detail, a dicarboxylic acid and a diol arefirst subjected to esterification reaction to form a low condensate (lowmolecular weight polyester), and the low condensate is then subjected todeglycolation reaction (liquid phase polycondensation) to increase themolecular weight. In some cases, solid phase polycondensation isperformed to further increase the molecular weight.

In the process for producing polyesters mentioned above, a conventionalantimony compound, a conventional germanium compound or the like is usedas a polycondensation catalyst.

However, the polyester produced by the use of the antimony compound as apolycondensation catalyst is inferior to the polyester produced by theuse of a germanium compound as a polycondensation catalyst in thetransparency and the heat resistance. In the use of the antimonycompound as a polycondensation catalyst, further, the acetaldehydecontent in the resulting polyester is desired to be decreased. On theother hand, the germanium compound is considerably expensive, so thatthe production cost of polyester becomes high. To decrease theproduction cost, a process including recovering the germanium compoundscattered during the polycondensation and reusing it has been studied.

By the way, it is known chat titanium is an element having a function ofpromoting polycondensation reaction of a low condensate. Titaniumcompounds such as titanium alkoxide, titanium tetrachloride, titanyloxalate and orthotitanic acid are publicly known as polycondensationcatalysts, and various studies have been made to utilize such titaniumcompounds as the polycondensation catalysts.

However, when the conventional titanium compounds are used as thepolycondensation catalysts, their activity is inferior to that of theantimony compound or the germanium compounds. In addition, the resultingpolyester has a problem of being markedly colored yellow, and hence theyhave not been put into practical use yet. In the industrial productionof polyesters using these titanium compounds as the polycondensationcatalysts, further, there is a problem of corrosion caused by elution ofchlorine content in case of catalysts containing a large amount ofchlorine, such as titanium tetrachloride and partial hydrolyzate oftitanium tetrachloride. Therefore, catalysts having low chlorine contentare sometimes desired.

Under such circumstances as described above, catalysts for polyesterproduction capable of producing polyesters with high polycondensationactivity or catalysts for polyester production capable of producing suchpolyesters as satisfy any one of requirements of low acetaldehydecontent, high transparency and excellent tint with high catalyticactivity are desired.

There are also desired a process for producing polyesters by whichpolyesters having desired intrinsic viscosity (IV) can be obtained for ashort period of time, a process for producing polyesters by whichpolyesters having low acetaldehyde content can be obtained with highpolymerization activity, and a process for producing polyesters by whichpolyesters having excellent tint can be obtained with highpolymerization activity.

As described above, the polyester, particularly polyethyleneterephthalate, is favorably used as a material of containers ofbeverages such as juice, soft drinks and carbonated beverages.

To produce a blow molded article from the polyester, the polyester isfed to a molding machine such as an injection molding machine to form apreform for a blow molded article, then the preform is inserted in amold of a given shape, and the preform is subjected to stretch blowmolding and a heat treatment (heat setting)

As for the molded product obtained from the conventional polyester suchas conventional polyethylene terephthalate, however, the content ofacetaldehyde is increased during the molding and the acetaldehyderemains in the resulting molded product, so that flavor or scent of thecontents filled in the molded product is sometimes considerablydeteriorated

As a process for producing polyethylene terephthalate having smallincrease of the acetaldehyde content during the molding, a process,which includes treating a particulate polyethylene terephthalate withwater vapor of 110° C. or higher prior to solid phase polycondensationof the polyethylene terephthalate, is disclosed in Japanese PatentLaid-Open Publication No 25815/1984, or a process for producingpolyethylene terephthalate of high polymerization degree, which includesa step of moisture controlling polyethylene terephthalate having anintrinsic viscosity of not less than 0.4 dl/g and a density of not morethan 1.35 g/cm³ to vary the moisture content to not less than 0.2% byweight, a step of precrystallizing the polyethylene terephthalate at atemperature of 140° C. or higher, and a step of solid phasepolymerization at a temperature of 180 to 240° C. in an inert gasatmosphere or reduced pressure, is disclosed in Japanese PatentLaid-Open Publication No. 219328/1984.

However, the increase of the acetaldehyde content in the polyethyleneterephthalate obtained by these processes cannot be lowered down below acertain level.

In Japanese Patent Laid-Open Publication No. 97990/ 1993, a method fortreating polyethylene terephthalate comprising bringing pellets ofpolyethylene terephthalate having been subjected to solid phasepolymerization into contact with a phosphoric acid aqueous solutionhaving a concentration of not less than 1 ppm is disclosed.

In this method, however, the phosphoric acid functions as an acedcatalyst to perform hydrolysis, and as a result, decrease of theintrinsic viscosity is accelerated during the melt molding.

The conventional polyester, e.g., polyethylene terephthalate, containsoligomers such as a cyclic trimer, and the oligomers such as a cyclictrimer adhere to an inner surface of a mold for blow molding or a gasexhaust vent or a gas exhaust pipe of a mold to cause stain of the mold,or adhere to a vent zone of an injection molding machine. The stain ofthe mold causes surface roughening or whitening of the resulting blowmolded article. The whitened blow molded article must be discarded. Inthe production of a blow molded article using the conventionalpolyester, the stain of the mold must be frequently removed, and thisresults in conspicuous lowering of productivity of the blow moldedarticle.

In addition, the polyester obtained by the use of the antimony compoundor the germanium compound as a polycondensation catalyst sometimes haslow melt flowability and is insufficient in the moldability.

Under such circumstances as described above, there is desired apolyester having a low acetaldehyde content, hardly increased in theacetaldehyde content during the molding and hardily causing stain of amold or a polyester having high melt flowability and excellentmoldability.

Further, there is also desired a polyester molded product havingexcellent transparency and tint or a molded product such as a blowmolded article preform or a blow molded article, e.g., a polyester blowmolded article having a low content of a cyclic primer.

One of the present applicants has found that the main cause of the stainof a mold in the molding process resides in that large amounts ofoligomers such as a cyclic trimer are produced in the molding of thepolyester to increase the total amount of the oligomers such as a cyclictrimer contained in the polyester, and has also found that the increaseof the oligomers such as a cyclic trimer can be remarkably inhibited bybringing polyester obtained through the solid phase polycondensationinto contact with water of the like, so they have proposed this inJapanese Patent Laid-Open Publication No. 283393/1996

OBJECT OF THE INVENTION

The present invention has been made in view of the prior arts asdescribed above, and it is an object of the invention to provide acatalyst for polyester production capable of producing a polyester withhigh catalytic activity or a catalyst for polyester production capableof producing such a polyester of high quality as satisfies any ore ofrequirements of a low acetaldehyde content, high transparency andexcellent tint with high catalytic activity.

It is another object of the invention to provide a process for producinga polyester by which a polyester having a desired intrinsic viscosity(IV) can be obtained for a short period of time, a process for producinga polyester by which a polyester having a low acetaldehyde content canbe produced with high polymerization activity, and a process forproducing a polyester by which a polyester having excellent tint can beobtained with high polymerization activity.

It is a further object of the invention to provide a polyester havingsmall increase of the acetaldehyde content during the molding,particularly a polyester having a low acetaldehyde content and smallincrease of the acetaldehyde content during the molding, a polyesterhardly bringing about stain of a mold, a polyester having excellenttransparency and tint, or a polyester having high melt flowability andexcellent moldability.

It is a still further object of the invention to provide a Polyestermolded product having excellent transparency and tint or a polyestermolded product such as a blow molded article prrform or a blow moldedarticle, e.g., a polyester blow molded article having a low content of acyclic trimer.

SUMMARY OF THE INVENTION

One embodiment of the catalyst for polyester production according to thepresent invention includes:

-   -   a catalyst for polyester production, comprising a solid titanium        compound (I-a) which is obtained by dehydro-drying a hydrolyzate        obtained by hydrolyzing a titanium halide and has a molar ratio        (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09        and less than 4;    -   a catalyst for polyester production, comprising a        titanium-containing solid compound (I-b) which is obtained by        dehydro-drying a hydrolyzate obtained by hydrolyzing a mixture        of a titanium halide and a compound of at least one element        selected from elements other than titanium or a precursor of the        compound and has a molar ratio (OH/Ti) of a hydroxyl group (OH)        to titanium (Ti) exceeding 0.09 and less than 4; and    -   a catalyst for polyester production, comprising:        -   (I) a polycondensation catalyst component comprising the            solid titanium compound (I-a) and/or the titanium-containing            solid compound (I-b), and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus.

Another embodiment of the catalyst for polyester production according tothe present invention includes:

-   -   a catalyst for polyester production, comprising:        -   (I) a polycondensation catalyst component comprising a solid            titanium compound (I-c) obtained by dehydro-drying a            hydrolyzate obtained by hydrolyzing a titanium halide, and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus;    -   a catalyst for polyester production, comprising a        titanium-containing solid compound (I-d) obtained by        dehydro-drying a hydrolyzate obtained by hydrolyzing a mixture        of a titanium halide and a compound of at least one element        selected from elements other than titanium or a precursor of the        compound; and    -   a catalyst for polyester production, comprising:        -   (I) a polycondensation catalyst component comprising the            titanium-containing solid compound (I-d), and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus.

In the catalyst for polyester production described above, theco-catalyst component (II) is preferably a magnesium compound.

A further embodiment of the catalyst for polyester production accordingto the present invention includes:

-   -   a catalyst for polyester production, comprising a solid titanium        compound (I-e) obtained by a process comprising bringing a        titanium halide into contact with water to hydrolyze the        titanium halide and thereby obtain an acid solution containing a        hydrolyzate of the titanium halide, rendering the solution basic        by the use of a base, then adjusting pH of the solution to 2 to        6 by the use of an acid, and dehydro-drying the resulting        precipitate;    -   a catalyst for polyester production, comprising a solid titanium        compound (I-f) obtained by a process comprising bringing a        titanium halide into contact with water to hydrolyze the        titanium halide and thereby obtain an acid solution containing a        hydrolyzate of the titanium halide, adjusting pH of the solution        to 2 to 6 by the use of a base, and dehydro-drying the resulting        precipitate;    -   a catalyst for polyester production, comprising:        -   (I) a polycondensation catalyst component comprising the            solid titanium compound (I-e) or the solid titanium compound            (I-f),and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus;    -   a catalyst for polyester production, comprising a        titanium-containing solid compound (I-g) obtained by a process        comprising bringing a mixture of a titanium halide and a        compound of at leas one element selected from elements other        than titanium or a precursor of the compound into contact with        water to hydrolyze the titanium halide and thereby obtain an        acid solution containing a hydrolyzate of the titanium halide,        rendering the solution basic by the use of a base, then        adjusting pH of the solution of 2 to 6 by the use of an acid,        and dehydro-drying the resulting precipitate;    -   a catalyst for polyester production, comprising a        titanium-containing solid compound (I-h) obtained by a. process        comprising bringing a mixture of a titanium halide and a        compound of at least one element selected from elements other        than titanium or a precursor of the compound into contact with        water to hydrolyze the titanium halide and thereby obtain an        acid solution containing a hydrolyzate of the titanium halide,        adjusting pH of the solution to 2 to 6 by the use of a base, and        dehydro-drying the resulting precipitate;    -   a catalyst for polyester production, comprising:        -   (I) a polycondensation catalyst component comprising the            titanium-containing solid compound (I-g) or (I-h), and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus

In the catalyst for polyester production described above, theco-catalyst component (II) is preferably a magnesium compound.

A still further embodiment of the catalyst for polyester productionaccording to the present invention includes:

-   -   a catalyst for polyester production, comprising a solid titanium        compound (I-i) which is obtained by dehydro-drying titanium        hydroxide and has a crystallinity, as calculated from an X-ray        diffraction pattern having 2θ (diffraction angle) of 18° to 35°,        of not more than 50%; and    -   a catalyst for polyester production, comprising:        -   (I) a polycondensation catalyst component comprising the            solid titanium compound (I-i), and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus.

A still further embodiment of the catalyst for polyester productionaccording to the present invention includes:

-   -   a catalyst for polyester production, comprising a slurry        obtained by heating a mixture of:        -   (A-1) a hydrolyzate (I-j) obtained by hydrolyzing a titanium            compound or a hydrolyzate (I-k) obtained by hydrolyzing a            mixture of a titanium compound and a compound of at least            one element selected from elements other than titanium or a            precursor of the compound,        -   (B) a basic compound, and        -   (C) an aliphatic diol.

In the catalyst for polyester production described above, the basiccompound (B) is preferably at least one compound selected fromtetraethylammonium hydroxide, tetraethylammonium hydroxide, aqueousammonia, sodium hydroxide, potassium hydroxide, N-ethylmorpholine andN-methylmorpholine.

The aliphatic diol (C) is preferably ethylene glycol.

A still further embodiment of the catalyst for polyester productionaccording to the present invention includes:

-   -   a catalyst for polyester production, comprising:        -   (A-2) a hydrolyzate (I-m) obtained by hydrolyzing a titanium            halide or a hydrolyzate (I-n) obtained by hydrolyzing a            mixture of a titanium halide and a compound of at least one            element selected from elements other than titanium or a            precursor of the compound, and        -   (D) a metallic phosphate containing at least one element            selected from beryllium, magnesium, calcium, strontium,            boron, aluminum, gallium, manganese, cobalt and zinc; and    -   a catalyst for polyester production, comprising a slurry        obtained by heating a mixture of:        -   (A-2) a hydrolyzate (I-m) obtained by hydrolyzing a titanium            halide or a hydrolyzate (I-n) obtained by hydrolyzing a            mixture of a titanium halide and a compound of at least one            element selected from elements other than titanium or a            precursor of the compound,        -   (E) a metallic compound containing at least one element            selected from beryllium, magnesium, calcium, strontium,            boron, aluminum, gallium, manganese, cobalt and zinc,        -   (F) at least one phosphorus compound selected from            phosphoric acid and phosphoric esters, and        -   (G) an aliphatic diol.

In the catalyst for polyester production described above, the metallicphosphate (D) is preferably magnesium hydrogenphosophate or trimagnesiumdiphosphate. Further, it is preferable that the metallic compound (E) isa magnesium compound, the phosphorus compound (F) is phosphoric acid ortrimethyl phosphate, and the aliphatic diol (G) is ethylene glycol.

The heating temperature of the mixture of the components (A-2), (E), (F)and (G) is preferably in the range of 100 to 200° C., and the heatingtime is preferably in the range of 3 minutes to 5 hours.

In the catalyst for polyester production according to the inventiondescribed above, the compound of at least one element selected fromelements other than titanium or the precursor of the compound is acompound of at leas one element selected from the group consisting ofberyllium, magnesium, calcium, strontium, barium, scandium, yttrium,lanthanum, zirconium, hafnium, vanadium, niobium, tantalum, chromium,molybdenum, tungsten, manganese, iron, ruthenium, cobalt, rhodium,nickel, palladium, copper, zinc, boron, aluminum, gallium, silicon,germanium, tin, antimony and phosphorus, or a precursor of the compound.

One embodiment of the process for producing a polyester according to thepresent invention is a process comprising polycondensing an aromaticdicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative thereof in the presence ofthe above-mentioned catalyst for polyester production.

Another embodiment of the process for producing a polyester according tothe present invention is a process comprising an esterification step inwhich an aromatic dicarboxylic acid or an ester=-forming derivativethereof and an aliphatic diol or an ester-forming derivative thereof areesterified to form a low condensate and a polycondensation step in whichthe low condensate is polycondensed in the presence of apolycondensation catalyst to increase the molecular weight, wherein:

-   -   the polycondensation catalyst used is a catalyst comprising:        -   (I) a polycondensation catalyst component comprising a            hydrolyzate (I-j) obtained by hydrolyzing a titanium            compound or a hydrolyzate (I-k) obtained by hydrolyzing a            mixture of a titanium compound and a compound of at least            one element selected from elements other than titanium or a            precursor of the compound, and        -   (II) a co-catalyst compound comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus; and    -   the polycondensation catalyst component (I) is added to the        esterification reactor before the beginning of the        esterification reaction or immediately after the beginning of        the esterification reaction.

In the process for producing a polyester described above, theco-catalyst component (II) is preferably a magnesium compound.

A further embodiment of the process for producing a polyester accordingto the present invention is a process comprising polycondensing anaromatic dicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative thereof in the presence ofa polycondensation catalyst selected from the following catalysts (1) to(3) and a phosphoric ester to produce a polyester;

-   -   (1) a polycondensation catalyst comprising a hydrolyzate (I-m)        obtained by hydrolyzing a titanium halide;    -   (2) a polycondensation catalyst comprising a hydrolyzate (I-n)        obtained by hydrolyzing a mixture of a titanium halide and a        compound of at least one element selected from elements other        than titanium or a precursor of the compound, and    -   (3) a polycondensation catalyst comprising:        -   the hydrolyzate (I-m) or (I-n), and        -   a compound of at least one element selected from beryllium,            magnesium, calcium, strontium, barium boron, aluminum,            gallium, manganese, cobalt, zinc, germanium and antimony, a            phosphate or a phosphite.

In the process for producing a polyester described above, the phosphoricester is preferably tributyl phosphate, trioctyl phosphate or triphenylphosphate.

A still further embodiment of the process for producing a polyesteraccording to the present invention is a process comprisingpolycondensing an aromatic dicarboxylic acid or an ester-formingderivative thereof and an aliphatic diol or an ester-forming derivativethereof in the presence of a polycondensation catalyst selected from thefollowing catalysts (1) to (3) and at least one compound selected fromcyclic lactone compounds and hindered phenol compounds to produce apolyester;

-   -   (1) a polycondensation catalyst comprising a hydrolyzate (I-m)        obtained by hydrolyzing a titanium halide,    -   (2) a polycondensation catalyst comprising a hydrolyzate (I-n)        obtained by hydrolyzing a mixture of a titanium halide and a        compound of at least one element selected from elements other        than titanium or a precursor of the compound, and    -   (3) a polycondensation catalyst comprising:        -   the hydrolyzate (I-m) or (I-n), and        -   a compound of at least one element selected from beryllium,            magnesium, calcium, strontium, barium, boron, aluminum,            gallium, manganese, cobalt, zinc, germanium and antimony, a            phosphate or a phosphite.

In the process for producing a polyester described above, at least onephosphorus compound selected from phosphoric acid and phosphoric esterscan be further used in combination.

The at least one compound selected from cyclic lactone compounds andhindered phenol compounds is preferably a mixture of5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one,tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methaneand tris(2,4-di-t-butylphenyl)phosphite.

A still further embodiment of the process for producing a polyesteraccording to the present invention is a process comprising anesterification step in which an aromatic dicarboxylic acid or anester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof are esterified to form a low condensateand a polycondensation step in which the low condensate is polycondensedin the presence of a polycondensation catalyst to increase the molecularweight, wherein:

-   -   the polycondensation catalyst used in a catalyst comprising:        -   (I) a polycondensation catalyst component comprising a            hydrolyzate (I-m) obtained by hydrolyzing a titanium halide            or a hydrolyzate (I-n) obtained by hydrolyzing a mixture of            a titanium halide and a compound of at least one element            selected from elements other than titanium or a precursor of            the compound, and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus; and    -   a tint adjusting agent is added in the esterification step of        the polycondensation step.

In the process for producing a polyester described above, the tintadjusting agent is preferably at least one agent selected from SolventBlue 104, Pigment Red 263, Solvent Red 135, Pigment Blue 29, PigmentBlue 15:1, Pigment Blue 15:3, Pigment Red 187 and Pigment Violet 19.

The co-catalyst component (II) is preferably a magnesium compound.

Embodiments of the method for treating a polyester according to thepresent invention include:

-   -   a method for treating a polyester, comprising bringing a        polyester, which is obtained by the use of a titanium compound        catalyst and in which the reaction has been completed, into        contact with a phosphorous acid aqueous solution, a        hypophosphorous acid aqueous solution, a phosphoric ester        aqueous solution, a phosphorous ester aqueous solution or a        hypophosphorous eater aqueous solution, each of said solutions        having a concentration of not less than 10 ppm in terms of        phosphorus atom;    -   a method for treating a polyester, comprising bringing a        polyester, which is obtained by the use of a titanium compound        catalyst and in which the reaction has been completed, into        contact with an organic solvent; and    -   a method for treating a polyester, comprising bringing a        polyester, which is obtained by the use of a titanium compound        catalyst and in which the reaction has been completed, into        contact with an organic solvent solution of phosphoric acid, an        organic solvent solution of a phosphoric ester, an organic        solvent solution of phosphorous acid, an organic solvent        solution of hypophosphorous ester or an organic solvent solution        of a hypophosphorous ester, each of said solutions having a        concentration of not less than 10 ppm in terms of phosphorus        atom.

The polyester preferably has an intrinsic viscosity of not less than0.50 dl/g, a density of not less than 1.37 g/cm³ and an acetaldehydecontent of not more than 5 ppm.

The organic solvent is a solvent selected from alcohols, saturatedhydrocarbons and ketones, preferably isopropanol or acetone.

The phosphoric ester is preferably tributyl phosphate, triphenylphosphate or trimethyl phosphate.

The polyester used in the above method is preferably polyethyleneterephthalate.

One embodiment of the polyester according to the present invention is apolyester (P-1) obtained by polycondensing an aromatic dicarboxylic acidor an ester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof in the presence of a catalyst forpolyester production which comprises:

-   -   (I) a polycondensation catalyst component comprising the solid        titanium compound (I-c) or the titanium-containing solid        compound (I-d), and    -   (II) a co-catalyst compound comprising a magnesium compound,    -   wherein the titanium content is in the range of 1 to 100 ppm,        the magnesium content is in the range of 1 to 200 ppm, and the        weight ratio (Mg/Ti) of magnesium to titanium is not less than        0.01.

The polyester (P-1) is preferably polyethylene terephthalate.

Another embodiment of the polyester according to the present inventionis a polyester (p-2) having the following properties:

-   -   a titanium atom is contained in an amount of 0.1 to 200 ppm,    -   a metal atom M selected from beryllium, magnesium, calcium,        strontium, barium, boron, aluminum, gallium, manganese, cobalt,        zinc and antimony is contained in an amount of 0.1 to 500 ppm,    -   the molar ratio (titanium atom/metal atom M) of the titanium        atom to the metal atom M is in the range of 1/50 to 50/1, and    -   a tint adjusting agent is contained in an amount of 0.01 to 100        ppm.

The polyester (P-2) is preferably polyethylene terephthalate.

A further embodiment of the polyester according to the present inventionis a polyester (p-3) having the following properties:

-   -   the intrinsic viscosity is not less than 0.50 dl/g, a titanium        atom is contained in an amount of 0.1 to 200 ppm,    -   a metal atom M selected from beryllium, magnesium, calcium,        strontium, barium, boron, aluminum, gallium, manganese, cobalt,        zinc and antimony is contained in an amount of 0.1 to 500 ppm,    -   the molar ratio (titanium atom/meal atom M) of the titanium atom        to the metal atom M is in the range of 0.05 to 50, and

The content of acetaldehyde is not more than 4 ppm, and when thisacetaldehyde content is taken as W₀ ppm and a content of acetaldehyde ina stepped square plate molded product obtained by heating said polyesterto a temperature of 275° C. to melt it and molding the molten polyesteris taken as W₁ ppm, the value of W₁−W₀ is not more than 10 ppm.

In the polyester (P-3), the titanium atom is preferably one derived froma polycondensation catalyst obtained by hydrolysis of a titanium halide.

The polyester (P-3) is preferably polyethylene terephthalate.

A still further embodiment of the polyester according to the presentinvention is a polyester (P-4) having the following properties:

-   -   the intrinsic viscosity is not less than 0.50 dl/g,    -   a titanium atom is contained in an amount of 0.1 to 200 ppm,    -   a metal atom M selected from beryllium, magnesium, calcium,        strontium, barium, boron, aluminum, gallium, manganese, cobalt,        zinc and antimony is contained in an amount of 0.1 to 500 ppm,    -   the molar ratio (titanium atom/metal atom M) of the titanium        atom to the metal atom M is in the range of 0.05 to 50, and    -   the content of a cyclic trimer is not more than 0.5% by weigh,        and when this cyclic trimer content is taken as x % by weight        and a content of a cyclic trimer in a stepped square plate        molded product obtained by heating said polyester to a        temperature of 290° C. to melt it and molding the molten        polyester is taken as y % by weight, x and y satisfy the        following relation        y≦−0.2x+0.2.

In the polyester (P-4), the titanium atom is preferably one derived froma polycondensation catalyst obtained by hydrolysis of a titanium halide.

The polyester (P-4) is preferably polyethylene terephthalate

A still further embodiment of the polyester according to the presentinvention is a polyester (P-5) having the following properties:

-   -   when the ratio (L/T) of a flow length (L) to a flow        thickness (T) in the injection molding of said polyester at        290° C. is taken as Y and the intrinsic viscosity of a molded        product obtained by the injection molding is taken as X (dl/g),        X and Y satisfy the following relation        Y≧647−500X.

The Polyester (P-5) is obtained by, for example, polycondensing anaromatic dicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative hereof in the presence of:

-   -   a polycondensation catalyst comprising a hydrolyzate (I-m)        obtained by hydrolyzing a titanium halide;    -   a polycondensation catalyst comprising a hydrolyzate (I-n)        obtained by hydrolyzing a mixture of a titanium halide and a        compound of at least one element selected from elements other        than titanium or a precursor of the compound, or    -   a polycondensation catalyst comprising:        -   (I) a polycondensation catalyst component comprising the            hydrolyzate (I-m) or the hydrolyzate (I-n), and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus.

The compound of at least one element selected from elements other thantitanium or the precursor of the compound is the same compound orprecursor as previously described.

The co-catalyst compound (II) is preferably a magnesium compound.

In the polyester (P-5), it is preferable that the titanium atom contentis in the range of 1 to 100 ppm, the magnesium atom content is in therange of 1 to 200 ppm, and the weight ratio (Mg/Ti) of the magnesiumatom to the titanium atom is not less than 0.01.

The polyester (P-5) is preferably polyethylene terephthalate.

One embodiment of the polyester molded product according to the presentinvention is a molded product obtained from the polyester (P-1), andexamples of the polyester molded products include a blow molded article,a film, a sheet and a fiber.

Another embodiment of the polyester molded product according to thepresent invention is a blow molded article obtained from the polyester(P-4) and having a cyclic trimer content of not more than 0.6% byweight.

A further embodiment of the polyester molded product according to thepresent invention is a blow molded article preform or a blow moldedarticle each of which is obtained from the polyester (P-5).

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows X-ray diffraction patterns to explain a method of measuringa crystallinity of a solid titanium compound.

FIG. 2 is a perspective view of a stepped square plate molded productused for measuring a haze, a content of a cyclic trimer and a content ofacetaldehyde.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst for polyester production according to the presentinvention, a process for producing a polyester using the catalyst, apolyester obtained by the process and uses of the polyester aredescribed in detail hereinafter.

One embodiment of the catalyst for polyester production according to theinvention comprises a solid titanium compound (I-a) and/or atitanium-containing solid compound (I-b) described below, and ifnecessary, a co-catalyst component (II) described below.

Solid Titanium Compound (7-a), Titanium-containing Solid Compound (7-b)

The solid titanium compound (I-a) of the invention is obtained byhydrolyzing a titanium halide and then dehydro-drying the resultinghydrolyzate.

The titanium halide is a compound having at least one titaniumatom-halogen atom bond in a molecule. Examples such compounds includetitanium tetrahalides, such as titanium tetrachloride, titaniumtetrabromide and titanium tetraiodide; titanium trihalides, such astitanium trichloride; titanium dihalides, such as titanium dichloride;and titanium monohalides.

There is no specific limitation on the method to hydrolyze the titaniumhalide, and for example, there can be mentioned (1) a method of addingthe titanium halide to water, (2) a method of adding water into thetitanium halide, (3) a method of passing a gas containing vapor of thetitanium halide through water, (4) a method of passing a gas containingwater vapor through the titanium halide, (5) a method of contacting agas containing the titanium halide with a gas containing water vapor.

In the present invention, the method of hydrolysis is not specificallylimited as described above, but in each method, it is necessary to allowa large excess of water to act on the titanium halide and therebycompletely carry out the hydrolysis. If the hydrolysis is not completelycarried out and if the resulting hydrolyzate is such a partialhydrolyzate as described in Japanese Patent Publication No. 19477/1976,the polycondensation rate may be insufficient.

The temperature for the hydrolysis is usually not higher than 100° C.,preferably in the range of 0 to 70° C.

The titanium-containing solid compound (I-b) of the invention isobtained by hydrolyzing a mixture of a titanium halide and a compound ofat least one element selected from elements other than titanium or aprecursor of the compound (sometimes referred to as a “compound ofanother element” hereinafter) and then dehydro-drying the resultinghydrolyzate. That is, the titanium compound is hydrolyzed in thepresence of a compound of another element, and the resulting precipitateis dried to obtain the titanium-containing solid compound (I-b)

The compound of another element is a compound of at least one elementselected from the group consisting of beryllium, magnesium, calcium,strontium, barium, scandium, yttrium, lanthanum, zirconium, hafnium,vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese,iron, ruthenium, cobalt, rhodium, nickel, palladium, copper, zinc,boron, aluminum, gallium, silicon, germanium, tin, antimony andphosphorus (each of these elements sometimes being referred to as“another element” hereinafter), or a precursor of the compound. Thecompound of another element is, for example, a hydroxide.

The compounds of another element can be used singly or in combination oftwo or more kinds.

There is no specific limitation on the method to hydrolyze the mixtureof the titanium halide and the compound of another element, and forexample, there can be mentioned (1) a method of adding the titaniumhalide to water in which the compound of another element has beendissolved or suspended, (2) a method of adding a mixture of the titaniumhalide and the compound of another element to water, (3) a method ofadding water to a mixture of the titanium halide and the compound ofanother element, (4) a method adding water, in which the compound ofanother element has been dissolved or suspended, to the titanium halide,(5) a method of passing a gas containing vapor of the titanium halidethrough water in which the compound of another element has beendissolved or suspended, (o6) a method of passing a gas containing vaporof the titanium halide and vapor of the compound of another elementthrough water, (7) a method of passing a gas containing water vaporthrough a mixture of the titanium halide and the compound of anotherelement, (8) a method of passing a gas containing water vapor and vaporof the compound of another element through the titanium halide, and (9)a method of contacting a gas containing the titanium halide, a gascontaining the compound of another element and a gas containing watervapor with one another.

In the hydrolysis, the molar ratio (E/Ti) of another element (E) in thecompound of another element to titanium (Ti) in the titanium halide isdesirably in the range of 1/50 to 50/1. The temperature for thehydrolysis is usually not higher than 100° C., preferably in the rangeof 0 to 70° C.

When the titanium halide or the mixture of the titanium halide and thecompound of another element is hydrolyzed, the resulting liquid exhibitsacidic property by virtue of hydrogen halide produced by the hydrolysisof the titanium halide. Because of the acidic property, the hydrolysisis not completed in some cased, so that a base may be added to performneutralization. Examples of the bases (sometimes referred to as“neutralizing base(s)” hereinafter) employable herein include aqueousammonia; hydroxides of Group 1 and Group 2 elements of the periodictable, such as sodium hydroxide, potassium hydroxide, magnesiumhydroxide; carbonate (hydrogencarbonate) compounds of Groud 1 and Group2 elements of the periodic table, such as sodium caronate, sodiumhydrogencarbonate, potassium carbonate and potassium hydrogencarbonate;urea; and basic organic compounds. At the end point of theneutralization, the pH value is preferably not less than 4, and theneutralization is preferably carried out at a temperature of not higherthan 70° C.

The hydrolyzate of the titanium halide or the hydrolyzate of the mixtureof the titanium halide and the compound of another element obtained bythe hydrolysis is, in this stage, a gel of a hydrous hydroxide(sometimes called “orthotitanic acid”) or a hydrous complex hydroxidegel. By dehydro-drying the hydrous hydroxide gel or the hydrous complexhydroxide gel, the solid titanium compound (I-a) or thetitanium-containing solid compound (I-b) according to the invention isobtained. Through the drying, a part of hydroxyl groups are removed.

The drying can be carried out at ordinary pressure or under reducedpressure in a state of solid phase or a state where the gel is suspendedin a liquid phase having higher boiling point than water. Although thedrying temperature is not specifically limited, it is preferably notlower than 30° C. and lower than 350° C. The hydrous hydroxide gel orthe hydrous complex hydroxide gel may be washed with water beforedrying, or the solid titanium compound or the titanium-containing solidcompound may be washed with water after drying, to remove water-solublecomponents. It is preferable to conduct the drying rapidly.

Although the composition of the solid titanium compound (I-a) or thetitanium-containing solid compound (I-b) obtained as above variesdepending upon presence or absence of another element, amount thereof,washing or non-washing, method of drying and degree of drying, the molarratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) is usually morethan 0.09 and less than 4, preferably in the range of 0.1 to 3, morepreferably in the range of 0.1 to 2. The molar ratio of a hydroxyl groupto titanium can be determined by measuring an absorbed water content anda thermally desorbed water content, and can be specifically determinedin the following manner.

In order to determine the hydroxyl group content, the absorbed watercontent is first measured by a Karl Fischer's water content meter. Then,the weight loss on heating up to 600° C. is measured bythermogravimetric analysis. By heating up to 600° C., the absorbed wateris desorbed. It is considered that the hydroxyl group is eliminated aswater, and therefore, the absorbed water content is subtracted from theweight loss on heating to obtain the hydroxyl group content. Thetitanium content in the titanium-containing solid compound is determinedby a high-frequency plasma emission analyzer (Inductively coupled plasmaspectroscopy). From the titanium content and the hydroxyl group content,the OH/Ti ratio is determined.

More specifically, in case of, for example, a solid titanium compoundprepared using ammonia as a neutralizing agent and having a titaniumcontent of 46% by weight, an absorbed water content of 6.73% by eight, aweight loss on heating up to 600° C. of 9.67% by weight, a nitrogencontent of 1.3% by weight and a chlorine content of 14 ppm, the OH/Tiratio is calculated as described below. The nitrogen cotnent is analyzedby an all nitrogen microanalyzer (chemiluminescence method), and thechlorine content is analyzed by chromatography.

The amount by mol of titanium in 100 g of the titanium-containing solidcompound is calculated as follows.46(Ti content)+47.88 (atomic weight of Ti)=0.9607

Nitrogen and chlorine the solid titanium compound are eliminated asammonia and hydrogen chloride, respectively, so that the thermallydesorbed water content (% by weight) is determined as follows.9.67(weight loss on 600° C. heating)−(1.3(nitrogen content)×(17/14)(interms of ammonia))−(0.0014 (chlorine content)×(36.5/35.5)(in terms ofhydrogen chloride))=8.090

From the calculation result and the measured value of the absorbed watercontent, the thermally desorbed water content (% by weight) derived fromthe hydroxyl group is determined as follows.8.090−6.73=1.360

From the above, the amount by mol of the hydroxyl group is determined asfollows.(1.360/18)×2 =0.1511

From the above, the molar ratio (OH/Ti) of the hydroxyl group content tothe titanium content in the solid titanium compound is determined asfollows.0.1511+0.9607=0.157

In the solid titanium compound (I-a) and the titanium-containing solidcompound (I-b), the hydroxyl group remains even at temperatures at whichthe polycondensation reaction is performed, e.g., about 280° C.

The fact that the solid titanium compound (I-a) and thetitanium-containing solid compound (I-b) have a OH/Ti ratio in the aboverange and that the hydroxyl group remains therein even at temperaturesat which the polycondensation reaction is performed, e.g., about 280°C., indicates that the solid titanium compound (I-a) and thetitanium-containing solid compound (I-b) are inherently different fromorthotitanic acid (represented by H₄TiO₄, titanium:hydroxyl group (bymol)=1:4) referred to in Japanese Patent Laid-Open Publication No.57291/1977 and Japanese Patent Publication 26597/1972, and areinherently different from titanium oxide used as a catalyst or polyesterproduction described in Japanese Patent Laid-Open Publication No.156595/1975, etc.

In the titanium-containing solid compound (I-b) according to theinvention, the molar ratio (E/Ti) of another element (E) to titanium(Ti) is in the range of 1/50 to 50/1, preferably 1/40 to 40/1, morepreferably 1/30 to 30/1.

In the solid titanium compound (I-a) and the titanium-containing solidcompound (I-b) according to the invention, the chlorine content is inthe range of usually 0 to 10000 ppm, preferably 0 to 100 ppm.

The solid titanium compound (I-a) or the titanium-containing solidcompound (I-b) is used in combination with a co-catalyst (II) comprisingthe following co-catalyst compound, if desired.

Co-catalyst Compound

The co-catalyst compound is a compound of at least one element selectedfrom the group consisting of beryllium, magnesium, calcium, strontium,barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium,antimony and phosphorus.

Examples of the compounds of at least one element selected from thegroup consisting of beryllium, magnesium, calcium, strontium, barium,boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimonyand phosphorus include aliphatic acid salts of these elements, such asacetates thereof; carbonates, sulfates and nitrates of these elements;halide of these elements, such as chlorides thereof; acetylacetonatosalts of these elements; and oxides of these elements. Of these,preferably are acetates and carbonates.

Examples of phosphorus compounds include phosphates and phosphites of atleast one metal selected from Group 1 and Group 2 of the periodic table,transition metals of Period 4 of the period table, zirconium, hafniumand aluminum.

The co-catalyst compounds employable in the invention are describedbelow more specifically.

Examples of aluminum compound include an aliphatic acid aluminum saltsuch as aluminum acetate, aluminum carbonate, aluminum chloride, and anacetylacetonato salt of aluminum. Of these, aluminum acetate andaluminum carbonate are particularly preferable.

Examples of barium compounds include an aliphatic acid barium salt suchas barium acetate, barium carbonate, barium chloride, and anacetylacetonato salt of barium. Of these, barium acetate and bariumcarbonate are particularly preferable.

Examples of cobalt compounds include an aliphatic acid cobalt salt suchas cobalt acetate, cobalt carbonate, cobalt chloride, and anacetylacetonato salt of cobalt. Of these, cobalt acetate and cobaltcarbonate are particularly preferable.

Examples of magnesium compounds include an aliphatic acid magnesium saltsuch as magnesium acetate, magnesium carbonate, magnesium chloride, andan acetylacetonato salt of magnesium. Of these, magnesium acetate andmagnesium carbonate are particularly preferable.

Examples of manganese compounds include an aliphatic acid manganese saltsuch as manganese acetate, manganese carbonate, manganese chloride, andan acetylacetonato salt of manganese. Of these, manganese acetate andmanganese carbonate are particularly preferable.

Examples of strontium compounds include an aliphatic acid strontium saltsuch as strontium acetate, strontium carbonate, strontium chloride, andan acetylacetonato salt of strontium. Of these, strontium acetate andstrontium carbonate are particularly preferable.

Examples of zinc compounds include an aliphatic acid zinc salt such aszinc acetate, zinc carbonate, zinc chloride, and an acetylacetonato saltof zinc. Of these, zinc acetate and zinc carbonate are particularlypreferable.

Examples of germanium compounds include germanium dioxide and germaniumacetate.

Examples of antimony compounds include antimony dioxide and antimonyacetate.

Examples of the phosphates as the phosphorus compounds include lithiumphosphate, lithium dihydrogenphosphate, dilithium hydrogenphosphate,sodium phosphate, sodium dihydrogenphosphate, disodiumhydrogenphosphate, potassium phosphate, potassium dihydrogenphosphate,dipotassium hydrogenphosphate, strontium phosphate, strontiumdihydrogenphosphate, distrontium hydrogenphosphate, zirconium phosphate,barium phosphate, aluminum phosphate and zinc phosphate. Of these,sodium phosphate, sodium hydrogenphosphate, disodium hydrogenphosphate,potassium phosphate, potassium dihydrogenphosphate and dipotassiumhydrogenphosphate are particularly preferably employed.

The phosphite as the phosphorus compound is a phosphite of at least onemetal selected from alkali metals, alkaline earth metals, transitionmetals of Period 4 of the periodic table, zirconium hafnium andaluminum. Examples of the phosphites include lithium phosphite, sodiumphosphate, potassium phosphite, strontium phosphite, zirconiumphosphite, barium phosphite, aluminum phosphite and zinc phosphite. Ofthese, sodium phosphite and potassium phosphite are particularlypreferably employed.

Of the above co-catalyst compounds, preferably are magnesium compounds,such as magnesium carbonate and magnesium acetate; calcium compounds,such as calcium carbonate and calcium acetate; and zinc compounds suchas zinc chloride and zinc acetate.

The co-catalyst compounds can be used singly or in combination of two ormore kinds as the co-catalyst component.

The co-catalyst component (II) is desirably used in such an amount thatthe molar ratio ((II/(I-a)) of the metal atom in he co-catalystcomponent (II) to titanium in the solid titanium compound (I-a) or themolar ratio ((II)/(I-b)) of the metal atom in the co-catalyst component(II) to titanium and another element in the titanium-containing solidcompound (I-b) is in the range of 1/50 to 50/1, preferably 1/40 to 40/1,more preferably 1/30 to 30/1. When a phosphorus compound such as aphosphate or a phosphite is used, the amount thereof is an amount interms of a metal atom contained in the phosphorus compound.

The production of a polyester using the above catalyst is carried out bythe process described later, and in the polycondensation reaction of theprocess, the solid titanium compound (I-a) or the titanium-containingsolid compound (I-b) is desirably used in an amount of 0.001 to 0.2% bymol, preferably 0.002 to 0.1% by mol, in terms of a metal atom, based onthe aromatic dicarboxylic acid units in the low condensate.

When the co-catalyst component (II) is used in addition to the solidtitanium compound (I-a) or the titanium-containing solid compound (I-b),the co-catalyst component (II) is desirably used in an amount of 0.001to 0.5% by mol, preferably 0.002 to 0.3% by mol, in terms of a metalatom, based on the aromatic dicarboxylic acid units in the lowcondensate.

The catalyst for polyester production comprising the solid titaniumcompound (I-a) and/or the titanium-containing solid compound (I-b), andoptionally, the co-catalyst component (II) is sufficient to be presentduring the polycondensation reaction. Therefore, the catalyst may beadded in any of a starting slurry preparation step, an esterificationstep and a liquid phase polycondensation step. Further, the total amountof the catalyst may be added a t once, or the catalyst may be addedplural times by portions. When the co-catalyst component (11) is used incombination, it may be added in a step identical with or different fromthe step where the solid titanium compound (I-a) or thetitanium-containing solid compound (1-b) is added.

The polyester obtained by the use of the above-mentioned catalyst forpolyester production is melt molded and used as blow molded articles(e.g., bottles), sheets, films, fibers, etc., but it is preferably usedas bottles.

The catalyst for polyester production described above can produce apolyester with higher catalytic activity as compared with a germaniumcompound or an antimony compound which has been heretofore used as apolycondensation catalyst. Further, when the catalyst for polyesterproduction is used, a polyester having more excellent transparency andtint and lower acetaldehyde content can be obtained as compared with thecase of using an antimony compound as a polycondensation catalyst.

Another embodiment of the catalyst for polyester production according tothe invention comprises a solid titanium compound (I-c) and aco-catalyst component (II) described below, or comprises atitanium-containing solid compound (I-d) and optionally a co-catalystcomponent (II) described below.

Solid Titanium Compound (I-c) T4Titanium-containing Solid Compound (T-d)

The solid titanium compound (I-c) or the invention is obtained byhydrolyzing a titanium halide and then dehydro-drying the resultinghydrolyzate.

Examples the titanium halides include the same titanium halide aspreviously described.

There is no specific limitation on the method to hydrolyze the titaniumhalide, and for example, the aforesaid methods (1) to (5) used in thepreparation of the solid titanium compound (I-a) are available.

In the present invention, the method of hydrolysis is not specificallylimited as described above, but in each method, it is preferable toallow a large excess of water to act on the titanium halide and therebycompletely carry out the hydrolysis. The temperature for the hydrolysisis usually not higher than 100° C., preferably in the range of 0 to 70°C.

The solid titanium compound (I-c) is used in combination with theaforesaid co-catalyst component (II) comprising the co-catalystcompound.

The titanium-containing solid compound (I-d) of the invention isobtained by hydrolyzing a mixture of the titanium halide and thecompound of another element previously described and then dehydro-dryingthe resulting hydrolyzate. That is, the titanium compound is hydrolyzedin the presence of the compound of another element, and the resultingprecipitate is subjected to solid-liquid separation, whereby thetitanium-containing solid compound (I-d) is obtained.

There is no specific limitation on the method to hydrolyze the mixtureof the titanium halide and the compound of another element, and forexample, the aforesaid methods (1) to (9) used in the preparation of thetitanium-containing solid compound (I-b) are available.

In the hydrolysis, the molar ratio (E/Ti) of the element (E) in thecompound of another element to titanium (T4) in the titanium halide isdesirably in the range of 1/50 to 50/1. The temperature for thehydrolysis is usually not higher than 100° C., preferably in the rangeof 0 to 70° C.

When the titanium halide or the mixture of the titanium halide and thecompound of another element is hydrolyzed, the resulting liquid exhibitsacidic property by virtue of hydrogen halide produced by the hydrolysisof the titanium halide. Because of the acidic property, the hydrolysisis not completed in some cases, so that the aforesaid neutralizing basemay be added to perform neutralization. At the end point of theneutralization, the pH value is preferably not less than 4, and theneutralization is preferably carried out at a temperature of not higherthan 70° C.

By dehydro-drying the hydrolyzate of the titanium halide or thehydrolyzate of the mixture of the titanium halide and the compound ofanother element obtained by the hydrolysis (hydrous hydroxide gel orhydrous complex hydroxide gel), the solid titanium compound (I-c) or thetitanium-containing solid compound (I-d) is obtained.

The drying can be carried out at ordinary pressure or under reducedpressure in a state of solid phase or a state where the gel is suspendedin a liquid phase having higher boiling point than water. Although thedrying temperature is not specifically limited, it is preferably notlower than 30° C. and lower than 350° C. The hydrous hydroxide gel orthe hydrous complex hydroxide gel may be washed with water beforedrying, or the solid titanium compound or the titanium-containing solidcompound may be washed with water after drying, to remove water-solublecomponents. It is preferable to conduct the drying rapidly.

Although the composition of the solid titanium compound (I-c) or thetitanium-containing solid compound (I-d) obtained as above variesdepending upon presence or absence of another element, amount thereof,washing or non-washing, method of drying and degree of drying, the molarratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) is usually morethan 0 and less than 4, preferably in the range of 0.001 to 3, morepreferably in, the range of 0.01 to 2. The molar ratio of a hydroxylgroup to titanium can be determined by the aforesaid method.

In the solid titanium compound (I-c) and the titanium-containing solidcompound (I-d), the hydroxyl group remains even at temperatures at whichthe polycondensation reaction is performed, e.g., about 280° C.

In the titanium-containing solid compound (I-d), the molar ratio (E/Ti)of another element (E) to titanium (Ti) is in the range of 1/50 to 50/1,preferably 1/40 to 40/1, more preferably 1/30 to 30/1.

In the solid titanium compound (I-c) and the titanium-containing solidcompound (I-d), the chlorine content is in the range of usually 0 to10000 ppm, preferably 0 to 100 ppm.

The solid titanium compound (I-c) is used in combination with theaforesaid co-catalyst component (II). The titanium-containing solidcompound (I-d) is used in combination with the co-catalyst component(II), if desired.

The co-catalyst component (II) is desirably used in such an amount thatthe molar ratio ((II)/(I-c)) of the metal atom in the co-catalystcomponent (II) to titanium in the solid titanium compound (I-c) or themolar ratio ((II)/(I-d)) of the metal atom in the co-catalyst component(II) to titanium and another element in the titanium-containing solidcompound (I-d) is in the range of 1/50 to 50/1, preferably 1/40 to 40/1,more preferably 1/30 to 30/1. When a phosphorus compound such as aphosphate or a phosphite is used, the amount thereof is an amount interms of a metal atom contained in the phosphorus compound. When amagnesium compound is used as the co-catalyst component (II), themagnesium compound is desirably used in such an amount that the weightratio (Mg/(I-c)) of Mg atom in the magnesium compound to titanium in thesolid titanium compound (I-c) or the weight ratio (Mg/(I-d)) of Mg atomin the magnesium compound to titanium and another element in thetitanium-containing solid compound (I-d) is not less than 0.01,preferably in the range of 0.06 to 10, particularly preferably in therange of 0.06 to 5. If the magnesium compound is used in the aboveamount, the resulting polyester has excellent transparency.

The production of a polyester using the above catalyst is carried out bythe process described later, and in the polycondensation reaction of theprocess, the solid titanium compound (I-c) or the titanium-containingsolid compound (I-d) is desirably used in an amount of 0.001 to 0.2% bymol, preferably 0.002 to 0.1% by mol, in terms of a metal atom, based onthe aromatic dicarboxylic acid units in the low condensate.

The amount of the co-catalyst component (II), which is used incombination with the solid titanium compound (I-c) or which isoptionally used when the titanium-containing solid compound (I-d) isused, is desired to be in the range of 0.001 to 0.5% by mol, preferably0.002 to 0.3% by mol, in terms of a metal atom, based on the aromaticdicarboxylic acid units in the low condensate.

The polyester produced by the use of the above catalyst for polyesterproduction, for example, polyethylene terephthalate, is excellent intint, particularly in transparency, and has a low content ofacetaldehyde.

The polyester obtained by the use of the above catalyst for polyesterproduction can be used as a material of various molded products Forexample, the polyester is melt molded and used as blow molded articles(e.g., bottles), sheets, films, fibers, etc., but it is particularlypreferably used as bottles.

In order to produce bottles, sheets, films, fibers, etc. from thepolyester such as polyethylene terephthalate, hitherto known processesare available.

The catalyst for polyester production described above can produce apolyester with higher catalytic activity as compared with a germaniumcompound or an antimony compound which has been heretofore used as apolycondensation catalyst. Further, when the catalyst for polyesterproduction is used, a polyester having more excellent transparency andtint and lower acetaldehyde content can be obtained as compared with thecase of using an antimony compound as a polycondensation catalyst.Moreover, polyethylene terephthalate obtained by the use of the catalystfor polyester production and molded products formed from thepolyethylene terephthalate have excellent transparency and tint and havea low content of acetaldehyde.

A farther embodiment of he catalyst for polyester production accordingto the invention comprises a solid titanium compound (I-e), a solidtitanium compound (7-f), the titanium-containing solid compound (I-g) ora titanium-containing solid compound (I-h) described below, andoptionally, a co-catalyst component (II) described below.

Solid Titanium Compound (I-e) or (I-f) Titanium-containing SolidCompound (I-g) or (I-h)

The solid titanium compound (I-e) of the invention is obtained by aprocess comprising bringing a titanium halide into contact with water tohydrolyze the titanium halide and thereby obtain an acid solutioncontaining a hydrolyzate of the titanium halide, rendering the solutionbasic by the use of a base, then adjusting pH of the solution to 2 to 6by the use of an acid, and dehydro-drying the resulting precipitate. Thesolid titanium compound (I-f) is obtained by a process comprisingbringing a titanium halide into contact with water to hydrolyze thetitanium halide and thereby obtain an acid solution containing ahydrolyzate of the titanium halide, adjusting pH of the solution to 2 to6 by the use of a base, and dehydro-drying the resulting precipitate.

Examples the titanium halides used for preparing the solid titaniumcompound (I-e) and the solid titanium compound (I-f) include the sametitanium halide as previously described.

In each of the processes to prepare the solid titanium compound (I-e)and the solid titanium compound (I-f), there is no specific limitationon the method to hydrolyze the titanium halide, and for example, theaforesaid methods (1) to (5) used in the preparation of the solidtitanium compound (I-a) are available.

In the present invention, the method of hydrolysis is not specificallylimited as described above, but in each method, it is preferable toallow a large excess of water to act on the titanium halide and therebycompletely carry out the hydrolysis. The temperature for the hydrolysisis usually not higher than 100° C., preferably in the range of 0 to 70°C.

By hydrolyzing the titanium halide as described above, an acid solutioncontaining a hydrolyzate of the titanium halide is obtained. The pH ofthe acid solution is usually about 1.

In the preparation of the solid titanium compound (I-e), the acidsolution containing the hydrolyzate is rendered basic (pH 9 to 12,preferably pH 9 to 11) by the use of a base and then adjusted to pH 2 to6, preferably pH 3 to 6, by the use of an acid. The temperature usedherein is usually not higher than 50° C., preferably not higher than 40°C. Adjustment of the solution to pH 2 to 6 results in a precipitate.

Examples of the bases include ammonia, sodium hydroxide, potassiumhydroxide, sodium carbonate and potassium carbonate. Of these, ammoniaand sodium hydroxide are preferable. Examples of the acids includeacetic acid and nitric acid. Of these, acetic acid is preferable.

When the acid solution containing the hydrolyzate is temporarily madebasic and then made acidic to form a precipitate as described above, thedehydration after solid-liquid separation can be carried out for a shortperiod of time. In addition, nitrogen, sodium, potassium or the likederived from the base hardly remains in the resulting solid titaniumcompound (I-e), and hence this solid titanium compound becomes acatalyst for polyester production having excellent polycondensationactivity and capable of producing a polyester of high quality.

In the preparation of the solid titanium compound (I-f), the acidsolution containing the hydrolyzate is adjusted to pH 2 to 6, preferablypH 3 to 6, by the use of a base. The temperature used herein is usuallynot higher than 50° C., preferably not higher than 40° C. Adjustment ofthe solution to pH 2 to 6 results in a precipitate.

Examples of the bases include the same bases as used in the preparationof the solid titanium compound (I-e). Of these, ammonia and sodiumhydroxide are preferable.

When the acid solution containing the hydrolyzate is adjusted to pH 2 to6 to form a precipitate as described above, the dehydration aftersolid-liquid separation can be carried out for a short period of time.In addition, nitrogen, sodium, potassium or the like derived from thebase hardly remains in the resulting solid titanium compound (I-f), andhence this solid titanium compound becomes a catalyst for polyesterproduction having excellent polycondensation activity and capable ofproducing a polyester of high quality.

In each of the processes to prepare the solid titanium compound (I-e)and the solid titanium compound (I-f), pH of the acid solution isadjusted to 2 to 6 to form a precipitate. This precipitate in this stageis a gel of a hydrous hydroxide sometimes called “orthotitanic acid”.She hydrous hydroxide gel is dehydro-dried to obtain the solid titaniumcompound (I-e) or the solid titanium compound (I-f) according to theinvention. Through the dehydro-drying, a part of the hydroxyl groupscontained in the hydrous hydroxide gel are removed.

As described above, pH of the acid solution is adjusted to 2 to 6 toform a precipitate, and the precipitate is subjected to solid-liquidseparation and then dried, whereby the solid titanium compound (I-e) orthe solid titanium compound (I-f) is obtained.

The drying is carried out at ordinary pressure or under reduced pressurein a state of solid phase or a state where the gel is suspended in aliquid phase having higher boiling point than water. Although the dryingtemperature is not specifically limited, it is preferably not lower than30° C. and lower than 350° C. The hydrous hydroxide gel may be washedwith water before drying, or the solid titanium compound (I-e) and thesolid titanium compound (I-f) may be washed with water after drying, toremove water-soluble components. It is preferable to conduct the dryingrapidly.

The titanium-containing solid compound (I-g) is obtained by a processcomprising bringing a mixture of a titanium halide and the aforesaidcompound of another element into contact with water to hydrolyze thetitanium halide and thereby obtain an acid solution containing ahydrolyzate of the titanium halide, rendering the solution basic by theuse of a base, then adjusting pH of the solution to 2 to 6 by the use ofan acid, and dehydro-drying the resulting precipitate. Thetitanium-containing solid compound (I-h) is obtained by a processcomprising bringing a titanium halide and a compound of at least oneelement selected from elements other than titanium or a precursor of thecompound into contact with water to hydrolyze the titanium halide andthereby obtain an acid solution containing a hydrolyzate of the titaniumhalide, adjusting pH of the solution to 2 to 6 by the use of a base, anddehydro-drying the resulting precipitate.

Examples the titanium halide used for preparing the titanium-containingsolid compound (I-g) and the titanium-containing solid compound (I-h)include the same titanium halide as previously described.

The compounds of another element can be used singly or in combination oftwo or more kinds.

In each of the processes to prepare the titanium-containing solidcompound (I-g) and the titanium-containing solid compound (I-h), thereis no specific limitation on the method to hydrolyze the mixture of thetitanium halide and the compound of another element, and for example,the aforesaid methods (1) to (9) used in the preparation of thetitanium-containing solid compound (I-b) are available.

In the present invention, the method of hydrolysis is not specificallylimited as described above, but in each method, it is preferable toallow a large excess of water to act on the mixture of the titaniumhalide and the compound of another element and thereby completely carryout the hydrolysis.

In the hydrolysis, the molar ratio (E/Ti) of the element (E) in thecompound of another element to titanium (Ti) in the titanium halide isdesirably in the range of 1/50 to 50/1. The temperature for thehydrolysis is usually not higher than 100° C., preferably in the rangeof 0 to 70° C.

By hydrolyzing the mixture of the titanium halide and the compound ofanother element as described above, an acid solution containing ahydrolyzate of the titanium halide and the compound of another elementis obtained. The pH of the acid solution is usually about 1.

In the preparation of the titanium-containing solid compound (I-g), theacid solution containing the hydrolyzate and the compound of anotherelement is rendered basic (pH 9 to 12, preferably pH 9 to 11) by the useof a base and then adjusted to pH 2 to 6, preferably pH 3 to 6, by theuse of an acid. The temperature used herein is usually not higher than50° C., preferably not higher than 40° C. Adjustment of the solution topH 2 to 6 results in a precipitate.

Examples of the bases include the same bases as used in the preparationof the solid titanium compound (I-e). Of these, ammonia and sodiumhydroxide are preferable. Examples of the acids include the same acidsas used in the preparation of the solid titanium compound (I-e). Ofthese, acetic acid is preferable.

When the acid solution containing the hydrolyzate and the compound ofanother element is temporarily made basic and then made acidic to form aprecipitate as described above, the dehydration after solid-liquidseparation can be carried out for a short period of time. In addition,nitrogen, sodium, potassium or the like derived from the base hardlyremains 4n the resulting titanium-containing solid compound (I-g), andhence this titanium-containing solid compound becomes a catalyst forpolyester production having excellent polycondensation activity andcapable of producing a polyester of high quality.

In the preparation of the titanium-containing solid compound (I-h), theacid solution containing the hydrolyzate and the compound of anotherelement is adjusted to pH 2 to 6, preferably pH 3 to 6, by the use of abase. The temperature used herein is usually not higher than 50° C.,preferably not higher than 40° C. Adjustment of the solution to pH 2 to6 result in a precipitate.

Examples of the bases include the same bases as used in the preparationof the solid titanium compound (I-e). Of these, ammonia and sodiumhydroxide are preferable.

When the acid solution containing the hydrolyzate and the compound ofanother element is adjusted to pH 2 to 6 to form a precipitate asdescribed above, the dehydration after solid-liquid separation can becarried out for a short period of time. In addition, nitrogen, sodium,potassium or the like derived from the base hardly remains in theresulting titanium-containing solid compound (I-h), and hence thistitanium-containing solid compound becomes a catalyst for polyesterproduction having excellent polycondensation activity and capable ofproducing a polyester of high quality.

In each of the processes to prepare the titanium-containing solidcompound (I-g) and the titanium-containing solid compound (I-h), pH ofthe acid solution is adjusted to 2 to 6 to form a precipitate. Thisprecipitate in this stage is a hydrous complex hydroxide gel containinga hydrous hydroxide sometimes called “orthotitanic acid”. The hydrouscomplex hydroxide gel is dehydro-dried to obtain the titanium-containingsolid compound (I-g) or the titanium-containing solid compound (I-h)according to the invention. Through the dehydro-drying, a part of thehydroxyl groups contained in the hydrous complex hydroxide gel areremoved.

The drying is carried out at ordinary pressure or under reduced pressurein a state of solid phase or a state where the gel is suspended in aliquid phase having higher boiling point than water. Although the dryingtemperature is not specifically limited, it is preferably not lower than30° C. and lower than 350° C. The hydrous complex hydroxide gel may bewashed with water before drying, or the titanium-containing solidcompound (I-g) and the titanium-containing solid compound (I-h) may bewashed with water after drying, to remove water-soluble components. Itis preferable to conduct the drying rapidly.

Although the composition of the solid titanium compound (I-e), the solidtitanium compound (I-f), the titanium-containing solid compound (I-g) orthe titanium-containing solid compound (I-h) obtained as above variesdepending upon presence or absence of another element, amount thereof,washing or non-washing, method of drying and degree of drying, the molarratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) is usually morethan 0.09 and less than 4, preferably in the range of 0.1 to 3, morepreferably in the range of 0.1 to 2. The molar ratio of a hydroxyl groupto titanium can be determined by measuring an absorbed water content anda thermally desorbed water content, specifically by the aforesaidmethod.

In the solid titanium compound (I-e), the solid titanium compound (I-f),the titanium-containing solid compound (I-g) and the titanium-containingsolid compound (I-h), the hydroxyl group remains even at temperatures atwhich the polycondensation reaction is performed, e.g., about 280° C.

In the titanium-containing solid compound (I-g) and thetitanium-containing solid compound(I-h), the molar ratio (E/Ti) ofanother element (E) to titanium (Ti) is in the range of 1/50 to 50/1,preferably 1/40 to 40/1, more preferably 1/30 to 30/1.

In the solid titanium compound (I-e), the solid titanium compound (I-f),the titanium-containing solid compound (I-g) and the titanium-containingsolid compound (I-h), the chlorine content is in the range of usually 0to 10000 ppm, preferably 0 to 100 ppm.

Examples of the co-catalyst components (II) optionally used incombination with the solid titanium compound (I-e), the solid titaniumcompound (I-f), the titanium-containing solid compound (I-g) or thetitanium-containing solid compound (I-h) include the same co-catalystcompounds as previously described. Of these, preferably are magnesiumcompounds such as magnesium carbonate and magnesium acetate; calciumcompounds such as calcium carbonate and calcium acetate; and zinccompounds such as zinc chloride and zinc acetate. The co-catalystcompounds can be used singly or in combination of two or more kinds.

The co-catalyst component (II) is desirably used in such an amount thatthe molar ratio ((II)/(I-e) or (I-f)) of the metal atom in theco-catalyst compound (II) to titanium in the solid titanium compound(I-e) or the solid titanium compound (I-f) or the molar ratio((II)/(I-g) or (I-h)) or the metal atom in the co-catalyst compound (II)to titanium and another element in the titanium-containing solidcompound (I-g) or the titanium-containing solid compound (I-h) is in therange of 1/50 to 50/1, preferably 1/40 to 40/1, more preferably 1/30 to30/1. When a phosphorus compound such as a phosphate or a phosphite isused, the amount thereof is an amount in terms of a metal atom containedin the phosphorus compound. When a magnesium compound is used as theco-catalyst component (II), the magnesium compound is desirably used insuch an amount that the weight ratio (Mg/(I-e) or (I-f)) of Mg atom inthe magnesium compound to titanium in the solid titanium compound (I-e)or the solid titanium compound (I-f) or the weight ratio (Mg/(I-g) or(I-h)) or Mg atom in the magnesium compound to titanium and anotherelement in the titanium-containing solid compound (I-g) or thetitanium-containing sold compound (I-h) is not less than 0.01,preferably in the range of 0.06 to 10, particularly preferably in therange of 0.06 to 5. If the magnesium compound is used in the aboveamount, the resulting polyester has excellent transparency.

The production of a polyester using the above catalyst is carried out bythe process described later, and in the polycondensation reaction, thesolid titanium compound (I-e), the solid titanium compound (I-f), thetitanium-containing solid compound (I-g) or the titanium-containingsolid compound (I-h) is desirably used in an amount of 0.001 to 0.2% bymol, preferably 0.002 to 0.1% by mol, in terms of a metal atom, based onthe aromatic dicarboxylic acid units in the low condensate.

When the co-catalyst component (II) is used in addition to the solidtitanium compound (I-e), the solid titanium compound (I-f), thetitanium-containing solid compound (I-g) or the titanium-containingsolid compound (I-h), the amount of the co-catalyst component (II) isdesired Lo be in the range of 0.001 to 0.5% by mol, preferably 0.002 to0.3% by mol, in terms of a metal atom, based on the aromaticdicarboxylic acid units in the low condensate.

The catalyst comprising one of the solid titanium compound (I-e), thesolid titanium compound (I-f), the titanium-containing solid compound(I-g) and the titanium-containing solid compound (I-h), and optionally,the co-catalyst component (II) is sufficient to be present during thepolycondensation reaction. Therefore, the catalyst may be added in anyof a starting slurry preparation step, an esterification step and aliquid phase polycondensation step. Further, the total amount of thecatalyst may be added at once, or the catalyst may be added plural timesby portions. When the co-catalyst component (II) is used in combination,it may be added in a step identical with or different from the stepwhere the solid titanium compound (I-e), the solid titanium compound(I-f), the titanium-containing solid compound (I-g) or thetitanium-containing solid compound (I-h) is added.

The catalyst for polyester production, particularly a catalystcomprising the solid titanium compound (I-e), the solid titaniumcompound (I-f), the titanium-containing solid compound (I-g) or thetitanium-containing solid compound (I-h) and the co-catalyst component(II) that is a magnesium compound, is favorable as a catalyst forproducing polyethylene terephthalate. In order to produce polyethyleneterephthalate using the catalyst comprising the solid titanium compound(I-e), the solid titanium compound (I-f), the titanium-containing solidcompound (I-g) or the titanium-containing solid compound (I-h) and themagnesium compound, for example, terephthalic acid or an ester-formingderivative thereof, ethylene glycol or an ester-forming derivativethereof, and optionally, an aromatic dicarboxylic acid other thanterephthalic acid and/or an aliphatic diol other than ethylene glycolare used as starting materials, and they are subjected toesterification, liquid phase polycondensation, and if necessary, solidphase polycondensation in accordance with the process described later.

In the production of polyethylene terephthalate, terephthalic acid or anester-forming derivative thereof is used in an amount of not less than80% by mol, preferably not less than 90% by mol, based on 100% by mol ofthe aromatic dicarboxylic acids, and ethylene glycol or an ester-formingderivative thereof is used in an amount of not less than 80% by mol,preferably not less than 90% by mol, based on 100% by mol of thealiphatic diols.

In the resulting polyethylene terephthalate, the titanium content ispreferably in the range of 1 to 200 ppm, particularly 1 to 100 ppm, andthe magnesium content is preferably in the range of 1 to 200 ppm,particularly 1 to 100 ppm. The weight ratio (Mg/Ti) of magnesium totitanium contained in the polyethylene terephthalate is desired to benot less than 0.01, preferably 0.06 to 10, particularly preferably 0.06to 5. In the polyethylene terephthalate, further, the chlorine contentis in the range of 0 to 1000 ppm, preferably 0 to 100 ppm.

The polyethylene terephthalate is excellent in tint, particularly intransparency, and has a low content of acetaldehyde. Such polyethyleneterephthalate is particularly preferably used for bottles.

The polyester obtained by the use of the above catalyst for polyesterproduction can be used as a material of various molded products. Forexample, the polyester is melt molded and used as blow molded articles(e.g., boggles), sheets, films, fibers, etc., but it is particularlypreferably used as bottles.

In order to produce bottles, sheets, films, fibers, etc. from thepolyester such as polyethylene terephthalate, hitherto known processesare available.

The catalyst for polyester production described above can produce apolyester with higher catalytic activity as compared with a germaniumcompound or an antimony compound which has been heretofore used as apolycondensation catalyst. Further, when the catalyst for polyesterproduction is used, a polyester having more excellent transparency andtint and lower acetaldehyde content can be obtained as compared with thecase of using an antimony compound as a polycondensation catalyst.

A still further embodiment of the catalyst for polyester productionaccording to the invention comprises a solid titanium compound (I-i)described below and if necessary a co-catalyst component (II) describedbelow.

Solid Titanium Compound (I-i)

The solid titanium compound (I-i) of the invention is obtained bydehydro-drying titanium hydroxide. The titanium hydroxide can beobtained by, for example, hydrolyzing a titanium compound.

The titanium compound used for the hydrolysis is, for example, atitanium halide or a titanium alkoxide.

Examples of the titanium halides include the same titanium halides aspreviously described. Examples of the titanium alkoxide include titaniumbutoxide and titanium tetraisopropoxide.

It is a preferred embodiment of the present invention to use a titaniumhalide as the titanium compound. The method of hydrolyzing the titaniumhalide is described below in detail, and hydrolysis of the titaniumalkoxide can be carried out in a manner similar to that described below.

There is no specific limitation on the method to hydrolyze the titaniumhalide, and for example, the aforesaid methods (1) to (5) used in thepreparation of the solid titanium compound (I-a) are available.

In the present invention, the method of hydrolysis is not specificallylimited as described above, but in each method, it is preferable toallow a large excess of water to act on the titanium halide and therebycompletely carry out the hydrolysis.

The temperature for the hydrolysis is usually not higher than 60° C.,preferably in the range of 0 to 50° C. When the hydrolysis is carriedout at the above temperature, a solid titanium compound having a lowcrystallinity tends to be obtained.

In the hydrolysis of the titanium halide, the compound of anotherelement previously described may be present. The compounds of anotherelement can be used singly or in combination of two or more kinds.

In the hydrolysis, the molar ratio (E/Ti) of another element (E) in thecompound of another element to titanium (Ti) in the titanium halide isdesirably in the range of 1/50 to 50/1. The temperature for thehydrolysis is usually not higher than 60° C., preferably in the range of0 to 50° C. When the hydrolysis is carried out at the above temperature,a solid titanium compound having a low crystallinity tends to beobtained.

When the titanium halide is hydrolyzed, the resulting liquid exhibitsacidic property by virtue of hydrogen halide produced by the hydrolysisof the titanium halide. Because of the acidic property, the hydrolysisis not completed in some cases, so that the aforesaid neutralizing basemay be added to perform neutralization. At the end point of theneutralization, the pH value is preferably not less than b 4, and theneutralization is desirably carried out at a temperature of not higherthan 60° C., preferably 0 to 50° C. When the neutralization is carriedout at the above temperature, a solid titanium compound having a lowcrystallinity tends to be obtained.

The compound containing titanium or the compound containing titanium andanother element obtained by the hydrolysis is, in this stage, a gel of ahydrous hydroxide (sometimes called “orthotitanic acid”).

In the present invention, the hydrous hydroxide gel is dehydro-dried togive a solid hydrolyzate (solid titanium compound). Through the drying,a part of hydroxyl groups are removed.

Drying of the hydrolyzate can be carried out at ordinary pressure orunder reduced pressure in a state of solid phase or a state where thehydrolyzate is suspended in a liquid phase having higher boiling pointthan water. Although the drying temperature is not specifically limited,it is preferably not lower than 30° C. and lower than 350° C.,particularly preferably in the range of 30 to 200° C. When the drying ofthe hydrolyzate is carried out at the above temperature, a solidtitanium compound having a low crystallinity tends to be obtained.

The hydrous hydroxide gel may be washed with water before drying, or thesolid titanium compound may be washed with water after drying, to removewater-soluble components. It is preferable to conduct the dryingrapidly.

The solid titanium compound (I-i) thus obtained has a crystallinity, ascalculated from an X-ray diffraction pattern having 2θ (diffractionangle) of 18° to 35°, of not more than 50%, preferably not more than45%, particularly preferably not more than 40%, or is amorphous. Thesolid titanium compound having the above crystallinity exhibitsexcellent activity as a polycondensation catalyst used for polyesterproduction.

The crystallinity of the solid titanium compound (I-i) is measured by,for example, the following method.

In FIG. 1, X-ray diffraction patterns to explain a method of measuring acrystallinity of a solid titanium compound are shown.

An X-ray diffraction pattern (FIG. 1(A)) of a sample and an X-raydiffraction pattern (FIG. 1(B)) of an amorphous solid titanium compoundare measured. Under the conditions that the base line is taken between18° and 35° and the position of 2θ (=28.5°, being a position which doesnot hinder the crystal peak) of the X-ray diffraction pattern of theamorphous solid titanium compound is taken as a base, the pattern ofFIG. 1(B) is reduced in the intensity direction so as to be overlappedwith the X-ray diffraction pattern of the sample, whereby a pattern ofFIG. 1(C) is drawn.

From the thus synthesized pattern, an area (I₀) of the X-ray diffractionpattern (except the background) of the sample within the diffractionangle range of 18° to 35° and an area (I_(a)) of the X-ray diffractionpattern (except the background) of the amorphous solid titanium compoundwithin the diffraction angle range of 18° to 35° are measured, and thecrystallinity (%) is determined as a value of (I₀−I_(a))/(I₀)×100.

Although the composition of the solid titanium compound (I-i) variesdepending upon presence or absence of another element, amount thereof,washing or non-washing, method of drying and degree of drying, the molarratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) is usually morethan 0.09 and less than 4, preferably in the range of 0.1 to 3, morepreferably in the range of 0.1 to 2, from the viewpoint ofpolymerization activity. The molar ratio of a hydroxyl group to titaniumcan be determined by measuring an absorbed water content and a thermallydesorbed water content, and can be specifically determined by theaforesaid method.

When the solid titanium compound (I-i) contains another element, themolar ratio (E/Ti) of another element (E) to titanium (Ti) in thiscompound is in the range of 1/50 to 50/1, preferably 1/40 to 40/1, morepreferably 1/30 to 30/1.

In the solid titanium compound (I-i), the chlorine content is in therange of usually 0 to 10000 ppm, preferably 0 to 100 ppm.

In the solid titanium compound (I-i), the hydroxyl group remains even attemperatures at which the polycondensation reaction is performed, e.g.,about 280° C.

The solid titanium compound (I-i) is used in combination with aco-catalyst component (II), if desired. Examples of the co-catalystcomponents (II) optionally used in combination include the sameco-catalyst compound as previously described. Of these, preferable aremagnesium compounds such as magnesium carbonate and magnesium acetate;calcium compounds such as calcium carbonate and calcium acetate; andzinc compounds such as zinc chloride and zinc acetate. The co-catalystcompounds can be used singly or in combination of two or more kinds.

The co-catalyst component (II) is desirably used in such an amount thatthe molar ratio (II)/(I-i)) of the metal atom in the co-catalystcomponent (II) to titanium (and another element if the solid titaniumcompound (I-i) contains another element) in the solid titanium compound(I-i) in the range of 1/50 to 50/1, preferably 1/40 to 40/1, morepreferably 1/30 to 30/1. When a phosphorus compound such as a phosphateor a phosphite is used, the amount thereof is an amount in terms of ametal atom contained in the phosphorus compound.

The production of a polyester using the above catalyst for polyesterproduction is carried out by the process described later, and in thepolycondensation reaction, the solid titanium compound (I-i) isdesirably used in an amount of 0.001 to 0.2% by mol, preferably 0.002 to0.1% by mol, in terms of a metal atom, based on the aromaticdicarboxylic acid units in the low condensate.

When the co-catalyst component (II) is used in addition to the solidtitanium compound (I-i), the amount of the co-catalyst component (II) isdesired to be in the range of 0.001 to 0.5% by mol, preferably 0.002 to0.3% by mol, in terms of a metal atom, based on the aromaticdicarboxylic acid units in the low condensate.

The catalyst comprising the solid titanium compound (I-i) and optionallythe co-catalyst component (II) is sufficient to be present during thepolycondensation reaction. Therefore, the catalyst may be added in anyof a starting slurry preparation step, an esterification step and aliquid phase polycondensation step. Further, the total amount of thecatalyst may be added at once, or the catalyst may be added plural timesby portions. When the co-catalyst component (II) is used in combination,it may be added in a step identical with or different from the stepwhere the solid titanium compound (I-i) is added.

The polyester obtained by the use of the above catalyst for polyesterproduction, preferably polyethylene terephthalate, is melt molded andused as blow molded articles (e.g., bottles), sheets, films, fibers,etc., but it is particularly preferably used as bottles.

The catalyst for polyester production described above can produce apolyester with higher catalytic activity as compared with a germaniumcompound or an antimony compound which has been heretofore used as apolycondensation catalyst. Further, when the catalyst for polyesterproduction is used, a polyester having more excellent transparency andtint and lower acetaldehyde content can be obtained as compared with thecase of using an antimony compound as a polycondensation catalyst.

A still further embodiment of the catalyst for polyester productionaccording to the invention comprises a slurry obtained by heating amixture of:

-   -   (A-1) a hydrolyzate (I-j) obtained by hydrolyzing a titanium        compound or a hydrolyzate (I-k) obtained by hydrolyzing a        mixture of a titanium compound and a compound of at least one        element selected from elements other than titanium or a        precursor of the compound (each hydrolyzate sometimes being        referred to as a “titanium-containing hydrolyzate (A-1)”        hereinafter),    -   (B) a basic compound, and    -   (C) an aliphatic diol.

Hydrolyzate (I-j) Hydrolyzate (I-k)

The hydrolyzate (I-j) is obtained by hydrolyzing a titanium compound,and the hydrolyzate (I-k) is obtained by hydrolyzing a mixture of atitanium compound and the aforesaid compound of another element.

The titanium compound used for the hydrolysis is, for example, atitanium alkoxide or a titanium halide, and particular examples thereofinclude the same compounds previously described.

It is a preferred embodiment of the present invention to use a titaniumhalide as the titanium compound. The method of preparing thetitanium-containing hydrolyzate using a titanium halide as the titaniumcompound is described below in detail, and preparation of a hydrolyzateof a titanium alkoxide can be carried out in a manner similar to thatdescribed below.

There is no specific limitation on the method to hydrolyze the titaniumhalide, and for example, the aforesaid methods (1) to (5) used in thepreparation of the solid titanium compound (I-a) are available.

In the present invention, the method of hydrolysis is not specificallylimited as described above, but in each method, it is preferable toallow a large excess of water to act on the titanium halide and therebycompletely carry out the hydrolysis. The temperature for the hydrolysisis usually not higher than 100° C., preferably in the range of 0 to 70°C.

The titanium-containing hydrolyzate (A-1) may be a hydrolyzate obtainedby hydrolyzing a mixture of the titanium halide and the aforesaidcompound of another element. That is, this hydrolyzate is obtained byhydrolyzing the titanium halide in the presence of the compound ofanother element. The compounds of another element can be used singly orin combination of two or more kinds.

There is no specific limitation on the method to hydrolyze the mixtureof the titanium halide and the compound of another element, and forexample, the aforesaid methods (1) to (9) used in the preparation of thetitanium-containing solid compound (I-b) are available.

In the hydrolysis, the molar ratio (E/Ti) of the element (E) in thecompound of another element to titanium (Ti) in the titanium halide isdesirably in the range of 1/50 to 50/1. The temperature for thehydrolysis is usually not higher than 100° C., preferably in the rangeof 0 to 70° C.

When the titanium halide or the mixture of the titanium halide and thecompound of another element is hydrolyzed, the resulting liquid exhibitsacidic property by virtue of hydrogen halide produced by the hydrolysisof the titanium halide. Because of the acidic property, the hydrolysisis not completed in some cases, so that the aforesaid neutralizing basemay be added to perform neutralizing. At the end point of theneutralization, the pH value is preferably not less than 4, and theneutralization is preferably carried out at a temperature of not higherthan 70° C.

The hydrolyzate (hydrous hydroxide gel or hydrous complex hydroxide gel)obtained by the hydrolysis can be per se used as a polycondensationcatalyst, but the hydrolyzate is preferably dehydro-dried to give asolid hydrolyzate (titanium-containing solid compound (I-k)).

Drying of the hydrolyzate can be carried out at ordinary pressure orunder reduced pressure in a state of solid phase or a skate where thehydrolyzate is suspended in a liquid phase having higher boiling pointthan water. Although the drying temperature is not specifically limited,it is preferably not lower than 30° C. and lower than 350° C. Thehydrous hydroxide gel or the hydrous complex hydroxide gel may be washedwith water before drying, or the titanium-containing solid compound(I-k) may be washed with water after drying, to remove water-solublecomponents. It is preferable to conduct the drying rapidly.

Although the composition of the titanium-containing solid compound (I-k)varies depending upon presence or absence of another element, amountthereof, washing or non-washing, method of drying and degree of drying,the molar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) isusually more than 0.09 and less than 4, preferably in the range of 0.1to 3, more preferably in the range of 0.1 to 2, from the viewpoint ofpolymerization activity. The molar ratio of a hydroxyl group to titaniumcan be determined by the aforesaid method.

In the titanium-containing solid component (I-k), the hydroxyl groupremains even at temperatures at which the polycondensation reaction isperformed, e.g., about 280° C.

When the titanium-containing solid compound (I-k) contains anotherelement, the molar ratio (E/Ti) of another element (E) to titanium (Ti)in this compound is in the range of 1/50 to 50/1, preferably 1/40 to40/1, more preferably 1/30 to 30/1.

In the titanium-containing hydrolyzate (A-1) such as the hydroushydroxide gel, the hydrous complex hydroxide gel or thetitanium-containing solid compound (I-k), the chlorine content is in therange of usually 0 to 10000 ppm, preferably 0 to 100 ppm.

Basic Compound (B)

The basic compound (B) is a compound which exhibits basic property inits aqueous solution, and examples of such compounds includetetraethylammonium hydroxide, tetramethylammonium hydroxide, aqueousammonia, sodium hydroxide, potassium hydroxide, N-ethylmorpholine andN-methylmorpholine. Of these, tetraethylammonium hydroxide ispreferable.

Aliphatic Diol (C)

Examples of the aliphatic diols (C) include ethylene glycol,trimethylene glycol, propylene glycol, tetramtheylene glycol, neopentylglycol, hexamethylene glycol and dodecamethylene glycol. Of these,ethylene glycol is preferably employed.

The catalyst for polyester production according to the invention isobtained as a slurry by heating a mixture of the titanium-containinghydrolyzate (A-1), the basic compound (B) and the aliphatic diol (C).

In the mixture liquid, the titanium-containing hydrolyzate (A-1) iscontained in an amount of 0.05 to 30% by weight, preferably 0.1 to 20%by weight, more preferably 0.5 to 15% by weight, the basic compound (B)is contained in an amount of 0.5 to 50% by weight, preferably 1 to 40%by weight, more preferably 2 to 30% by weight, and the residue is thealiphatic diol.

When the amount of the titanium-containing hydrolyzate (A-1) is not lessthan 0.05% by weight, the amount of the aliphatic diol (C) can bedecreased, whereby the polymerization rate becomes high. When the amountof the titanium-containing hydrolyzate is not more than 30% by weight,coloring of the mixture is little during the heating, and as a result,the tint of a polyester produced by the use of this catalyst becomesgood.

When the amount of the basic compound (B) is not less than 0.5% byweight, the catalytic activity is enhanced. When the amount of the basiccompound is not more than 50% by weight, coloring of the mixture islittle during the heating.

The heating temperature of the mixture is in the range of usually 100 to300° C., preferably 120 to 250° C., more preferably 140 to 200° C., andthe heating time is in the range of 5 minutes to 10 hours, preferably 30minutes to 8 hours.

The production of a polyester using the above catalyst for polyesterproduction is carried out by the process described later, and thecatalyst for polyester production is used in an amount of usually 0.0005to 0.2% by weight, preferably 0.001 to 0.05% by weight, in terms ofweight of a metal in the catalyst, based on the weight of the mixture ofthe aromatic dicarboxylic acid and the aliphatic diol.

The catalyst for polyester production can be fed to the polymerizationreactor in the esterification reaction step, or can be fed to thereactor in the first stage of the polycondensation reaction step.

In addition to the catalyst for polyester production of the invention,the aforesaid co-catalyst compound can be used as a co-catalystcomponent. Preferred examples of the co-catalyst components includemagnesium compounds such as magnesium carbonate and magnesium acetate;calcium compounds such as calcium carbonate and calcium acetate; andzinc compound such as zinc chloride and zinc acetate. The co-caltaytcompounds can be used singly or in combination of two or more kinds.

The co-catalyst component is desirably used in such an amount that themolar ratio ((M)/(Ti)) of the metal atom (M) in the co-catalystcomponent to titanium (and another element if the catalyst containsanother element) (Ti) in the catalyst for polyester production is in therange of 1/50 to 50/1, preferably 1/40 to 40/1, more preferably 1/30 to30/1. When a phosphorus compound such as a phosphate or a phosphite isused, the amount thereof is an amount in terms of a metal atom containedin the phosphorus compound.

The co-catalyst component can be fed to the polymerization reactor inthe esterification reaction step, or can be fed to the reactor in thefirst stage of the liquid phase polycondensation reaction step. When theco-catalyst component is fed in the esterification reaction step, theco-catalyst component can be added at the same time as the catalyst forpolyester production or separately.

When the catalyst for polyester production is used, a polyester having adesired intrinsic viscosity is obtained for a short period of time.

A still further embodiment of the catalyst for polyester productionaccording to the invention comprises:

-   -   (A-2) a hydrolyzate (I-m) obtained by hydrolyzing a titanium        halide or a hydrolyzate (I-n) obtained by hydrolyzing a mixture        of a titanium halide and a compound of at least one element        selected from elements other than titanium or a precursor of the        compound (each hydrolyzate sometimes being referred to as a        “titanium-containing hydrolyzate (A-2)” hereinafter), and    -   (D) a metallic phosphate containing at least one element        selected from beryllium, magnesium, calcium, strontium, boron,        aluminum, gallium, manganese, cobalt and zinc;        or comprises a slurry obtained by heating a mixture of:    -   (A-2) a hydrolyzate (I-m) obtained by hydrolyzing a titanium        halide or a hydrolyzate (I-n) obtained by hydrolyzing a mixture        of a titanium halide and a compound of at Least one element        selected from elements other than titanium or a precursor of the        compound,    -   (E) a metallic compound containing at least one element selected        from beryllium, magnesium, calcium, strontium, boron, aluminum,        gallium, manganese, cobalt and zinc,    -   (F) at least one phosphorus compound selected from phosphoric        acid and phosphoric esters, and    -   (G) an aliphatic diol.

Hydrolyzate (I-m). Hydrolyzate (I-n)

The hydrolyzate (I-m) is obtained by hydrolyzing a titanium halide, andthe hydrolyzate (I-n) is obtained by hydrolyzing a mixture of a titaniumhalide and the aforesaid compound of another element.

Examples of the titanium halides employable for the preparation of thetitanium-containing hydrolyzate (A-2) include the same titanium halidesas previously described.

There is no specific limitation on the me:hod to hydrolyze the titaniumhalide, and for example, the aforesaid methods (1) to (5) used in thepreparation of the solid titanium compound (I-a) are available.

In the present invention, the method of hydrolyses is not specificallylimited as described above, but in each method, it is preferable toallow a large excess of water to act on the titanium halide and therebycompletely carry out the hydrolysis. The temperature for the hydrolysisis usually not higher than 100° C., preferably in the range of 0 to 70°C.

The titanium-containing hydrolyzate (A-2) may be a hydrolyzate obtainedby hydrolyzing a mixture of the titanium halide and the aforesaidcompound of another element. That is, this hydrolyzate is obtained byhydrolyzing the titanium halide in the presence of the compound ofanother element. The compounds of another element can be used singly orin combination of two or more kinds.

There is no specific limitation on the method to hydrolyze the mixtureof the titanium halide and the compound of another element, and forexample, the aforesaid methods (1) to (9) used in the preparation of thetitanium-containing solid compound (I-b) are available.

In the hydrolysis, the molar ratio (E/Ti) of the element (E) in thecompound of another element o titanium (Ti) in the titanium halide isdesirably in the range of 1/50 to 50/1. The temperature for thehydrolysis is usually not higher than 100° C., preferably in the rangeof 0 to 70° C.

When the titanium halide or the mixture of the titanium halide and thecompound of another element is hydrolyzed, the resulting liquid exhibitsacidic property by virtue of hydrogen halide produced by the hydrolysisof the titanium halide. Because of the acid property, the hydrolysis isnot completed in some cases, so that the aforesaid neutralizing base maybe added to perform neutralization. At the end point of theneutralization, the pH value is preferably not less than 4, and theneutralization is preferably carried out at a temperature of not higherthan 70° C.

The hydrolyzate (hydrous hydroxide gel or hydrous complex hydroxide gel)obtained by the hydrolysis can be per se used as a polycondensationcatalyst, but the hydrolyzate is preferably dehydro-dried to give asolid hydrolyzate (titanium-containing solid compound (A-2)).

Drying of the hydrolyzate can be carried out at ordinary pressure orunder reduced pressure in a state of a solid phase or a state where thehydrolyzate is suspended in a liquid phase having higher boiling pointthan water. Although the drying temperature is not specifically limited,it is preferably not lower than 30° C. and lower than 350° C. Thehydrous hydroxide gel or the hydrous complex hydroxide gel may be washedwith water before drying, or the titanium-containing solid component(A-2) may be washed with water after drying, to remove water-solublecomponents. It is preferable to conduct the drying rapidly.

Although the composition of the titanium-containing solid compound (A-2)obtained above varies depending upon presence or absence of anotherelement, amount thereof, washing or non-washing, method of drying anddegree of drying, the molar ratio (OH/Ti) of a hydroxyl group (OH) totitanium (Ti) is usually more than 0.09 and less than 4, preferably inthe range of 0.1 to 3, more preferably in the range of 0.1 to 2, fromthe viewpoint of polycondensation activity. The molar ratio of ahydroxyl group to titanium can be determined by the aforesaid method.

In the titanium-containing solid compound (A-2), the hydroxyl groupremains even at temperatures at which the polycondensation reaction isperformed, e.g., about 280° C.

When the titanium-containing solid compound (A-2) contains anotherelement, the molar ratio (E/Ti) of another element (E) to titanium (Ti)in this compound is in the range of 1/50 to 50/1, preferably 1/40 to40/1, more preferably 1/30 to 30/1.

In the titanium-containing hydrolyzate (A-2) such as the hydroushydroxide gel, the hydrous complex hydroxide gel or thetitanium-containing solid compound (A-2), the chlorine content is in therange of usually 0 to 10000 ppm, preferably 0 to 100 ppm.

Metallic Phosphate (D)

The metallic phosphate (D) is a compound containing at least one elementselected from beryllium, magnesium, calcium, strontium, boron, aluminum,gallium, manganese, cobalt and zinc.

Examples of the metallic phosphates (D) include:

-   -   magnesium phosphate, such as magnesium hydrogenphosphate,        trimagnesium diphosphate and magnesium phosphite;    -   calcium phosphates, such as calcium hydrogenphosphate, calcium        dihydrogenphosphate and tricalcium phosphate;    -   strontium phosphates, such as strontium hydrogenphosphate;    -   aluminum phosphates, such as aluminum phosphate;    -   manganese phosphates, such as manganese dihydrogenphosphate and        manganese phosphate;    -   cobalt phosphates, such as cobalt phosphate; and    -   zinc phosphates, such as zinc phosphate.

Of these, magnesium phosphates are preferable, and magnesiumhydrogenphosphate and trimagnesium diphosphate are particularlypreferable.

The production of a polyester using the above catalyst for polyesterproduction is carried out by the process described later, and in thepolycondensation reaction, the titanium-containing hydrolyzate (A-2) isused in an amount of usually 0.0005 to 0.2% by mol, preferably 0.001 to0.05% by mol, in terms of a metal atom in the titanium-containinghydrolyzate (A-2), based on the amount by mol of the aromaticdicarboxylic acid (in terms of the aromatic dicarboxylic acid) in thelow condensate; and the metallic phosphate (D) is used in an amount ofusually 0.001 to 0.200% by mol, preferably 0.002 to 0.050% by mol, interms of phosphorus atom. When the amount of the titanium-containinghydrolyzate (A-2) and the metallic phosphate (D) are within the aboveranges, the catalyst exhibits high polymerization activity and theresulting polyester has a low acetaldehyde content.

The acetaldehyde content referred to herein is determined in thefollowing manner. A sample of 2 g is pulverized under cooling, and thetemperature of the sample is returned to room temperature. Then, 1 g ofthe sample is charged in a container, and 2 cc of an internal standardliquid is added to the container, followed by closing the container.Then, extraction is performed in an oven at 120° C. for 1 hour. Theextract is ice cooled, and the acetaldehyde content in 5 μl of thesupernatant liquid is measured by GC-6A manufactured by ShimadzuSeisakusho K.K. to determine the acetaldehyde content in the sample.

The titanium-containing hydrolyzate (A-2) can be fed to the reactor inthe esterification reaction step, or can be fed to the reactor in thefirst stage of the liquid phase polycondensation reaction step. Themetallic phosphate (D) can be fed to the reactor in the esterificationreaction step, or can be fed to the reactor in the first stage of theliquid phase polycondensation reaction step. The metallic phosphate (D)can be added at the same time as the titanium-containing hydrolyzate(A-2) or separately.

Metallic Compound (E)

The metallic compound (E) for use in the invention is a compoundcontaining at least one element selected from beryllium, magnesium,calcium, strontium, boron, aluminum, gallium, manganese, cobalt andzinc.

Examples of the metallic compounds (E) include:

-   -   magnesium compound, such as magnesium acetate, magnesium        carbonate and magnesium hydroxide;    -   calcium compounds, such as calcium hydroxide, calcium acetate        and calcium carbonate;    -   strontium compounds, such as strontium acetate and strontium        carbonate;    -   aluminum compounds, such as aluminum acetate, aluminum hydroxide        and aluminum carbonate;    -   manganese compounds, such as manganese acetate;    -   cobalt compounds, such as cobalt acetate; and    -   zinc compounds, such as zinc acetate.

Of these, magnesium compounds are preferable, and magnesium acetate andmagnesium carbonate are particularly preferable.

Phosphorus Compound (F)

Examples of the phosphorus compounds (II) for use in the inventioninclude phosphoric acid, and phosphoric esters, such as trimethylphosphate, triethyl phosphate, tri-n-butyl phosphate, trioctylphosphate, triphenyl phosphate and tricresyl phosphate. Of these,phosphoric acid and trimethyl phosphate are preferable.

Aliphatic Diol (G)

Examples of the aliphatic diols (G) for use in the invention includeethylene glycol, trimethylene glycol, propylene glycol, tetramethyleneglycol, neopentyl glycol, hexamethylene glycol and dodecamethyleneglycol. Of these, ethylene glycol is preferable.

The catalyst for polyester production according to the invention may bea catalyst obtained as a slurry by heating a mixture of thetitanium-containing hydrolyzate (A-2), the metallic compound (E), thephosphorus compound (F) and the aliphatic diol (G).

In the mixture liquid, the titanium-containing hydrolyzate (A-2) iscontained in an amount of 0.1 to 30% by weight, preferably 0.2 to 20% byweight, more preferably 0.3 to 10% by weight, in terms of titanium atom,the metallic compound (E) is contained in an amount of 0.1 to 30% byweight, preferably 0.2 co 20% by weight, more preferably 0.3 to 10% byweight, in terms of a metal, the phosphorus compound (a) is contained inan amount of 0.1 to 30% by weight, preferably 0.2 to 20% by weight, morepreferably 0.3 to 10% by weight, in terms of phosphorus atom, and theresidue is the aliphatic diol (G). The titanium-containing hydrolyzate(A-2) and the metallic compound (E) are preferably used in the sameamounts from the viewpoint of polymerization activity.

Heating of the mixture is performed for the purpose of allowing at leasta part of the metallic compound (E) dissolved in the aliphatic diol toreact with at least a part of the phosphorus compound (F) dissolved inthe aliphatic diol. Therefore, the amount of the metallic compound (E)and the phosphorus compound (F) is preferably no: more than 30% byweight from the viewpoint of solubility in the aliphatic diol.

The temperature for heating the mixture, though varies depending uponthe boiling point of the aliphatic diol, is in the range of usually 50to 200° C., preferably 80 to 190° C., more preferably 100 to 190° C.,and the heating time is in the range of 3 minutes to 5 hours, preferably30 minutes to 4 hours, more preferably 1 to 4 hours.

When the heating temperature is not lower than 50° C., the metalliccompound (E) dissolved in the aliphatic diol and the phosphorus compound(F) dissolved in the aliphatic diol easily undergo reaction. When theheating temperature is not higher than 200° C., the aliphatic diolhardly undergoes side reaction such as dehydration reaction.

The production of a polyester using the above catalyst for polyesterproduction is carried out by the process described later, and in thepolycondensation reaction, the slurry catalyst for polyester productionis used in an amount of usually 0.0005 to 0.2% by weight, preferably0.001 to 0.05% by weight, in terms of weight, of a metal (derived fromthe titanium-containing hydrolyzate (A-2)) in the catalyst, based on theweight of a mixture of terephthalic acid and ethylene glycol.

The slurry catalyst for polyester production can be fed to thepolymerization reactor in the esterification reaction step, or can befed to the reactor in the first stage of the polycondensation reactionsteps.

In the present invention, in addition to the catalyst for polyesterproduction comprising the titanium-containing hydrolyzate (A-2) and themetallic phosphate (D) or the slurry catalyst for polyester production,the aforesaid co-catalyst compound can be used as a co-catalystcomponent. Preferred examples of the co-catalyst compounds includemagnesium compound such as magnesium carbonate and magnesium acetate;calcium compounds such as calcium carbonate and calcium acetate; andzinc compounds such as zinc chloride and zinc acetate. The co-catalystcompounds can be used singly or in combination of two or more kinds.

The co-catalyst component is desirably used in such an amount that themolar ratio ((M)/(Ti)) of the metal atom (M) in the co-catalystcomponent to titanium (and another element if the catalyst containsanother element) (Ti) in the catalyst for polyester production is in therange of 1/50 to 50/1, preferably 1/40 to 40/1, more preferably 1/30 to30/1.

The co-catalyst component can be fed to the reactor in theesterification reaction step, or can be fed to the reactor in the firststage of the liquid phase polycondensation reaction step. When theco-catalyst component is fed in the esterification reaction step, theco-catalyst component can be added at the same time as the catalyst forpolyester production or separately.

The catalyst for polyester production according to the invention canproduce a polyester having a low acetaldehyde content with highpolymerization activity.

Next, the process for producing a polyester using the catalyst forpolyester production mentioned above is described.

Process for Producing Polyester

In the process for producing a polyester using the catalyst forpolyester production mentioned above, an aromatic dicarboxylic acid oran ester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof are polycondensed in the presence ofany one of the above-mentioned catalysts for polyester production. Oneembodiment of the process is described below.

Starting Materials

In the process for producing a polyester according to the invention, anaromatic dicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative thereof are used asstarting materials.

Examples of the aromatic dicarboxylic acids include terephthalic aced,phthalic acid, isophthalic acid, naphthalenedicarboxylic acid,diphenyldicarboxylic acid and diphenoxyethanedicarboxylic acid.

Examples of the aliphatic diols include aliphatic glycols, such asethylene glycol, trimethylene glycol, propylene glycol, tetramethyleneglycol, neopentyl glycol, hexamethylene glycol and dodecamethyleneglycol.

In the present invention, aliphatic dicarboxylic acids such as adipicacid, sebacic acid, azelaic acid and decanedicarboxylic acid, andalicyclic dicarboxylic acids such a cyclohexanedicarboxylic acid areemployable as starting materials together with the aromatic dicarboxylicacid. Further, alicyclic glycols such as cyclohexanedimethanol, andaromatic diols such as bisphenol, hydroquinone,2,2-bis(4-β-hydroxyethoxyphenyl)propanes, 1,3-bis(2-hydroxyethoxy)benzene and 1,4-bis(2-hydroxyethoxy)benzene are employable as startingmaterials together with the aliphatic diol.

In the present invention, moreover, polyfunctional compounds such astrimesic acid, trimethylolethane, trimethylolpropane, trimethylolmethaneand pentaerythritol are employable as starting materials.

Esterification Step

In the production of a polyester, first, the aromatic dicarboxylic acidor an ester-forming derivative thereof and the aliphatic diol or anester-forming derivative thereof are esterified.

More specifically, a slurry containing the aromatic dicarboxylic acid oran ester-forming derivative thereof and the aliphatic diol or anester-forming derivative thereof is prepared.

In the slurry, the aliphatic diol or an ester-forming derivative thereofis contained in an amount of usually 1.005 to 1.4 mol, preferably 1.01to 1.3 mol, more preferably 1.03 to 1.3 mol., based on 1 mol of thearomatic dicarboxylic acid or an ester-forming derivative thereof. Theslurry is continuously fed to the esterification reaction step.

The esterification reaction is carried out under reflux of ethyleneglycol using an apparatus consisting of two or more esterificationreactors connected in series, while water which is produced by thereaction is removed from the system by means of a rectification tower.

The esterification reaction is generally carried out in plural stages,and the esterification reaction or the first stage is carried out at areaction temperature of usually 240 to 270° C., preferably 245 to 265°C., under a pressure of 0.2 to 3 kg/cm²-G, preferably 0.5 to 2 kg/cm²-G,and the esterification reaction of the last stage is carried out at areaction temperature of usually 250 to 280° C., preferably 255 to 275°C., under a pressure of 0 to 1.5 kg/cm²-G, preferably 0 to 1.3 kg/cm²-G.

When the esterification reaction is carried out in two stages, theesterification reaction conditions of the first and the second stagesare as described above, and when the esterification reaction is carriedout in three or more stages, the esterification reaction conditions of.the second stage to the stage of last but one are between the reactionconditions of the first stage and the reaction conditions of the laststage.

For example, when the esterification reaction is carried out in threestages, the esterification reaction temperature of the second stage isin the range of usually 245 to 275° C., preferably 250 to 270° C., andthe pressure of this stage is in the range of usually 0 to 2 kg/cm²-G,preferably 0.2 to 1.5 kg/cm²-G.

There is no specific limitation on the degree of esterification in eachstage, but it is preferable that the increase of the degree ofesterification is smoothly distributed in each stage, and it isdesirable that the degree of esterification of the esterifiactionreation product in the last stage reaches usually not less than 90%,prefearlby not less than 93%.

It is possible to carry out the esterification reaction without addingadditives other than the aromatic dicarboxylic acid and the aliphaticdiol, and it is also possible to carry out the esterification reactionin the presence of the catalyst for polyester production describedabove. It is preferable to add a small amount of a basic compound and tocarry out the esterification reaction, because the proportion ofdioxyethylene terephthalate constituent units in the main chain ofpolyethylene terephthalate can be held at a relatively low level.Examples of the basic compounds employable herein include tertiaryamines, such as trimethylamine, tri-n-butylamine andbenzyldimethylamine; quaternary ammonium hydroxides, such astetraethylammonium hydroxide, tetra-n-butylammonium hydroxide andtrimethylbenzylammonium hydroxide; and other basic compounds, such aslithium carbonate, sodium carbonate, potassium carbonate and sodiumacetate.

Through the esterification reaction step, an esterification product (lowcondensate) is obtained, and the esterification product has anumber-average molecular weight of usually 500 to 5000. The lowcondensate thus obtained is then fed to a polycondensation (liquid phasepolycondensation) step.

Liquid Phase Polycondensation Step

In the liquid phase polycondensation step, the low-condensate obtainedin the esterification step is heated under reduced pressure at atemperature of not lower than the melting point of a polyester (usually250 to 280° C.) in the presence of the aforesaid polycondensationcatalyst, to polycondensate the low condensate. The polycondensationreaction is desirably carried out with distilling off the unreactedaliphatic diol from the reaction system.

The polycondensation reaction may be carried out in one stage or pluralstages. For example, when the polycondensation reaction is carried outin plural stages, the polycondensation reaction of the first stage iscarried out at a reaction temperature of 250 to 290° C., preferably 260to 280° C., under a pressure of 500 to 20 Torr, preferably 200 to 30Torr, and the polycondensation reaction of the last stage is carried outat a reaction temperature of 265 to 300° C., preferably 270 to 295° C.,under a pressure of 10 to 0.1 Torr, preferably 5 to 0.5 Torr.

When the polycondensation reaction is carried out in two stages, thepolycondensation reaction conditions of the first and the second stagesare as described above, and when the polycondensation reaction iscarried out in three or more stages, the polycondensation reactionconditions of the second stage to the stage of last but one are betweenthe reaction conditions of the first stage and the reaction conditionsof the last stage. For example, when the polycondensation reaction iscarried out in three stages, the polycondensation reaction of the secondstage is carried out at a reaction temperature of usually 260 to 295°C., preferably 270 to 285° C., under a pressure of usually 50 to 2 Torr,preferably 40 to 5 Torr. There is no specific limitation on theintrinsic viscosity reached in each stage of the polycondensationreaction step, but it is preferable that the increase of the intrinsicviscosity is smoothly distributed in each stage.

The polycondensation reaction is desirably carried out in the presenceof a stabilizer. The stabilizer is, for example, a phosphorus compound,and specific examples thereof include phosphoric esters, such astrimethyl phosphate, tiehtyl phosphate, tri-n-butyl phosphate, trioctylphosphate and triphenyl phosphate; phosphorus esters, such as triphenylphosphate, trisdodecyl phosphite and trisnonylphenyl phosphite; andother phosphoric esters, such as monomethyl phosphate, dimethylphosphate, monoethyl phosphate, diethyl phosphate, monoisopropylphosphate, diisopropyl phosphate, dibutyl phosphate, monobutyl phosphateand dioctyl phosphate; phosphoric acid; and polyphosphoric acid.

The phosphorus compound is desirably added in an amount of 0.005 to 0.2%by mol, preferably 0.01 to 0.1% by mol, in terms of phosphorus atom inthe phosphorus compound, based on the aromatic dicarboxylic acid. Thephosphorus compound may be fed in the esterification reaction step, ormay be fed to the reactor in the first stage of the polycondensationreaction step.

The polyester obtained in the liquid phase polycondensation stepdesirably has an intrinsic viscosity of 0.40 to 1.0 dl/g, preferably0.50 to 0.90 dl/g, more preferably 0.55 to 0.75 dl/g. There is nospecific limitation on the intrinsic viscosity reached in each of thestages except the last stage of the polycondensation step, but it ispreferable that the increase of the intrinsic viscosity is smoothlydistributed in each stage.

The intrinsic viscosity referred to herein is calculated from a solutionviscosity determined by heating 1.2 g of a polyester in 15 cc ofo-chlorophenol to melt it, then cooling the solution and measuring itsviscosity at 25° C.

The polyester desirably has a density of usually 1.33 to 1.35 gl/cm³.The density of the polyester referred to herein is measured at atemperature of 23° C. by means of a density gradient tube using a mixedsolvent of carbon tetrachloride and heptane.

The polyester obtained in the polycondensation step is generally meltextruded into particles (chips). The particulate polyester desirably hasan average particle diameter of usually 2.0 to 5.0 mm, preferably 2.2 to4.0 mm.

The polyester obtained in the liquid phase polycondensation step can bethen subjected to solid phase polycondensation, if desired.

Solid Phase Polycondensation Step

Before the particulate polyester is fed to the solid phasepolycondensation step, it may be heated at a temperature lower than thetemperature for the solid phase polycondensation to performprecrystallization.

The precrystallization can be carried out by heating the particulatepolyester at a temperature of usually 120 to 200° C., preferably 130 to180° C., for 1 minute to 4 hours, in a dry state. The precrystallizationmay be carried out by heating the particulate polyester at a temperatureof 120 to 200° C. for 1 minute or more in an atmosphere of water vapor,an atmosphere of an inert gas continuing water vapor or an atmosphere ofair containing water vapor.

The polyester thus precrystallized desirably has a crystallinity of 20to 50%.

In the precrystallization treatment, the “solid phase polycondensationreaction” of the polyester does not proceed, so that the intrinsicviscosity of the precrystallized polyester is almost equal to that ofthe polyester after the liquid phase polycondensation, and thedifference between the intrinsic viscosity of the precrystallizedpolyester and the intrinsic viscosity of the polyester beforeprecrystallization is usually not more than 0.06 dl/g.

The solid phase polycondensation step consists of at least one stage,and the solid phase polycondensation reaction is carried out at atemperature of 190 to 230° C., preferably 195 to 225° C., under apressure of 1 kg/cm²-G to 10 Torr, preferably atmospheric pressure to100 Torr, in an atmosphere of an inert gas such as nitrogen, argon orcarbonic acid gas. The inert gas used herein is desirably a nitrogengas.

The particulate polyester obtained after the solid phasepolycondensation may be subjected to water treatment by the methoddescribed in, for example, Japanese Patent Publication No. 64920/1995.This water treatment is carried out by contacting the particulatepolyester with water, water vapor, an inert gas containing water vapor,air containing water vapor or the like.

The intrinsic viscosity of the particulate polyester obtained as aboveis desired to be usually not less than 0.50 dl/g, preferably 0.60 to1.00 dl/g, more preferably 0.75 to 0.95 dl/g.

The production of the polyester comprising the esterification step andthe polycondensation step may be carried out batchwise, semicontinuouslyor continuously. The density of the polyester is desired to be usuallynot less than 1.37 g/cm³, preferably not less than 1.38 g/cm³, morepreferably not less than 1.39 g/cm³.

The polyester produced as above may contain additives hitherto known,such as stabilizer, release agent, antistatic agent, dispersant andcolorant (e.g., dye, pigment). These additives may be added in any stepof the process for producing the polyester, or may be added by forming amasterbatch before molding.

The polyester obtained by the invention can be used as a material ofvarious molded products. For example, the polyester is melt molded andused as blow molded articles (e.g., bottles), sheets, films, fibers,etc., but it is particularly preferably used as bottles.

In order to produce bottles, sheets, films, fibers, etc. from thepolyester obtained by the invention, such as polyethylene terephthalate,hitherto known processes are available.

Another embodiment of the process for producing a polyester according tothe invention is described below.

This embodiment is a process for producing a polyester, comprising anesterification step in which an aromatic dicarboxylic acid or anester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof are esterified to form a low condensateand a polycondensation step in which the low condensate is polycondensedin the presence of a polycondensation catalyst to increase the molecularweight, wherein:

-   -   the polycondensation catalyst used is a catalyst comprising:        -   (II) a catalyst component comprising a hydrolyzate (I-j)            obtained by hydrolyzing a titanium compound or a hydrolyzate            (I-k) obtained by hydrolyzing a mixture of a titanium            compound and a compound of at least one element selected            from elements other than titanium or a precursor of the            compound, and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus; and        -   the catalyst component (II) is added to the esterification            reactor before the beginning of the esterification reaction            or immediately after the beginning of the esterification            reaction.

The hydrolyzate (I-j) obtained by hydrolyzing a titanium compound andthe hydrolyzate (I-k) obtained by hydrolyzing a mixture of a titaniumcompound and a compound of at least one element selected from elementsother than titanium or a precursor of the compound are the same as thehydrolyzate (I-j) and the hydrolyzate (I-K) previously described,respectively.

Examples of the co-catalyst components (II) include the same co-catalystcompounds as previously described. Of these, preferable are magnesiumcompounds such as magnesium carbonate and magnesium acetate; calciumcompounds such as calcium carbonate and calcium acetate; and zinccompounds such as zinc chloride and zinc acetate. The co-catalystcompounds can be used singly or in combination of two or more kinds.

The production of a polyester comprising an esterification stem in whichan aromatic dicarboxylic acid or an ester-forming derivative thereof andan aliphatic diol or an ester-forming derivative thereof are esterifiedto form a low condensate and a polycondensation step in which the lowcondensate is polycondensed in the presence of a polycondensationcatalyst to increase the molecular weight is carried out through theesterification step, the liquid phase polycondensation step, and ifnecessary, the solid phase polycondensation step, as described above.However, the polycondensation of the esterification product fed to theliquid phase polycondensation step is conducted in the presence of apolycondensation catalyst comprising:

-   -   (II) a polycondensation catalyst compound comparing the        hydrolyzate (I-j) or the hydrolyzate (I-k), and    -   (II) a co-catalyst component.

Of the above components, the polycondensation catalyst compound (II) isadded to the reactor before the beginning of the esterification reactionor immediately after the beginning of the esterification reaction. Theexpression “immediately after the beginning of the esterificationreaction” used herein means a state where the degree of esterificationis not more than 50%. The term “degree of esterification” means a degreeof conversion of the aromatic dicarboxylic acid such as dicarboxylicacid, and the degree of esterification is expressed in a ratio betweenthe acid value (AV) and the saponification value of the reactionproduct.

On the other hand, the co-catalyst component (II) can be added to thereactor in any stage of the esterification reaction step, or can beadded to the reactor in the first stage of the liquid phasepolycondensation reaction step. When the co-catalyst component (II) isfed in the esterification reaction step, the co-catalyst component (II)may be added at the same time as the catalyst component (II) orseparately.

The catalyst compound (II) is used in an amount of usually 0.0005 to0.2% by weight, preferably 0.001 to 0.05% by weight, in terms of weightof a metal in the catalyst compound (II), based on the weight or amixture of the aromatic dicarboxylic acid and the aliphatic diol.

The co-catalyst component (II) s desirably used in such an amount thatthe molar ratio ((M)/)I-j)) of the metal atom (M) in the co-catalystcomponent (II) to titanium in the catalyst component (I-j) or the molarratio ((M)/(I-k)) of the metal atom (M) in the co-catalyst component(II) to titanium and another element in the catalyst compound (I-k) isin the range of 1/50 to 50/1, preferably 1/40 to 40/1, more preferably1/30 to 30/1. When a phosphorus compound such as a phosphate or aphosphite is used, the amount thereof is an amount in terms of a metalatom contained in the phosphorus compound.

According to the present invention, a polyester having a desiredintrinsic viscosity can be obtained for a short period of time.

A further embodiment of the process for producing a polyester accordingto the invention is described below.

This embodiment is a process for producing a polyester, comprisingpolycondensing an aromatic dicarboxylic acid or an ester-formingderivative thereof and an aliphatic diol or an ester-forming derivativethereof in the presence of a polycondensation catalyst selected from thefollowing catalysts (1) to (3) and a phosphoric ester to produce apolyester;

-   -   (1) a polycondensation catalyst comprising a hydrolyzate (I-m)        obtained by hydrolyzing a titanium halide,    -   (2) a polycondensation catalyst comprising a hydrolyzate (I-n)        obtained by hydrolyzing a mixture of a titanium halide and a        compound of at least one element selected from elements other        than titanium or a precursor of the compound, and    -   (3) a polycondensation catalyst comprising:        -   the hydrolyzate (I-m) or (I-n), and        -   a compound of at least one element selected from beryllium,            magnesium, calcium, strontium, barium, boron, aluminum,            gallium, manganese, cobalt, zinc, germanium and antimony, a            phosphate or a phosphite.

The hydrolyzate (I-m) obtained by hydrolyzing a titanium halide and thehydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halideand a compound of at least one element selected from elements other thantitanium or a precursor of the compound are the same as the hydrolyzate(I-m) and the hydrolyzate (I-n) previously described, respectively.

Examples of the compound of at least one element selected from the groupcomprising of beryllium, magnesium, calcium, strontium, barium, boron,aluminum, gallium, manganese, cobalt, zinc, germanium and antimony, thephosphate or the phosphite (sometimes referred to as a “co-catalystcompound (IIa)” hereinafter) include the same compounds as previouslydescribed with respect to the co-catalyst compounds. Such compounds canbe used singly or in combination of two or more kinds. Preferredexamples of the co-catalyst component (IIa) include magnesium compoundssuch as magnesium carbonate and magnesium acetate; calcium compoundssuch as calcium carbonate and calcium acetate; and zinc compounds suchas zinc chloride and zinc acetate.

Examples of the phosphoric esters used in combination with thepolycondensation catalyst in the polycondensation reaction includetrimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctylphosphate, triphenyl phosphate and tricresyl phosphate.

The production of a polyester comprising polycondensing an aromaticdicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative is carried out through theesterification step, the liquid phase polycondensation step, and ifnecessary, the solid phase polycondensation step, as described above.

The hydrolyzate (I-m) or (I-n) is used in an amount of usually 0.0005 to0.2% by weight, preferably 0.001 to 0.05% by weight, in terms of weightof a metal in the polycondensation catalyst, based on the weight of amixture of the aromatic dicarboxylic acid and the aliphatic diol.

The phosphoric ester is used in an amount of usually 0.001 to 0.1% byweight. Preferably 0.002 to 0.02% by weight, in terms of phosphorusatom. When the amounts of the hydrolyzate (I-m) or (I-n) and thephosphoric ester are within the above ranges, the effect of shorteningthe polycondensation time is high.

The co-catalyst component (IIa) is desirably used in such an amount thatthe molar ratio ((M)/(I-m)) of the metal atom (M) in the co-catalystcomponent (IIa) to titanium in the hydrolyzate (I-m) or the molar ratio((M)/(I-n)) of the metal atom (M) in the co-catalyst component (IIa) totitanium and another element in the hydrolyzate (I-n) is in the range of1/50 to 50/1, preferably 1/40 to 40/1, more preferably 1/30 to 30/1.When a phosphors compound such as a phosphate or a phosphite is used,the amount thereof is an amount in terms of a metal atom contained inthe phosphorus compound.

The polycondensation catalyst and the phosphoric ester can be fed to anystage of the esterification reaction step, or can be fed in the reactorin the first stage of the polycondensation reaction step.

According to the present invention, a polyester having a desiredintrinsic viscosity can be obtained for a short period of time.

A still further embodiment of the process for producing a polyesteraccording to the invention is described below.

This embodiment is a process for producing a polyester, comprisingpolycondensing an aromatic dicarboxylic acid or an ester-formingderivative thereof and an aliphatic diol or an ester-forming derivativethereof in the presence of a polycondensation catalyst selected from thefollowing catalysts (1) to (3) and at least one compound selected fromcyclic lactone compounds and hindered phenol compounds to produce apolyester;

-   -   (1) a polycondensation catalyst comprising a hydrolyzate (I-m)        obtained by hydrolyzing a titanium halide,    -   (2) a polycondensation catalyst comprising a hydrolyzate (I-n)        obtained by hydrolyzing a mixture of a titanium halide and a        compound of at least one element selected from elements other        than titanium or a precursor of the compound, and    -   (3) a polycondensation catalyst comprising:        -   the hydrolyzate (I-m) or (I-n), and        -   a compound of at least one element selected from beryllium,            magnesium, calcium, strontium, barium, boron, aluminum,            gallium, manganese, cobalt, zinc, germanium and antimony, a            phosphate or a phosphite.

The hydrolyzate (I-m) obtained by hydrolyzing a titanium halide and thehydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halideand a compound of at least one element selected from elements other thantitanium or a precursor of the compound are the same as the hydrolyzate(I-m) and the hydrolyzate (I-n) previously described, respectively.

The compound of at least one element selected from beryllium, magnesium,calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt,zinc, germanium and antimony, the phosphate or the phosphite is the sameas the co-catalyst component (IIa) described above. Preferred examplesof the co-catalyst components (IIa) include magnesium compounds such asmagnesium carbonate and magnesium acetate; calcium compounds such ascalcium carbonate and calcium acetate; and zinc compounds such as zincchloride and zinc acetate.

At least one compound selected from cyclic lactone compounds andhindered phenol compounds used in the polycondensation reaction is, forexample,

-   -   5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one,    -   tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane,    -   tris(2,4-di-t-butylphenyl)phosphite,    -   bis(2,6-di-t-butyl-4-phenylmethyl)pentaerythritol-diphosphite,    -   3,5-di-t-butyl-4-hydroxybenzylphosphoric acid distearyl ester,    -   2,6-di-t-butylphenol,    -   3,5-di-t-butyl-4-hydroxytoluene,    -   n-octadecyl-3-(4′-hydroxy-3′, 5′-di-t-butylphenyl)propionate,    -   tris(3,5-di-t-butyl-4-hydroxyphenyl)phosphite,    -   triphenyl phosphite, or    -   tetrakis(2,4-di-t-butylphenly)-4,4′-biphenylene diphosphite.

These cyclic lactone compounds and hindered phenol compounds can be usedsingly or in combination.

At least one compound selected from cyclic lactone compounds andhindered phenol compounds is preferably a mixture of5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one,tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methaneand tris(2,4-di-t-butylphenyl)phosphite.

The production of a polyester comprising polycondensing an aromaticdicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative is carried out through theesterification step, the liquid phase polycondensation step, and ifnecessary, the solid phase polycondensation step, as described above.

The hydrolyzate (I-m) or (I-n) is used in an amount of usually 0.0005 to0.2% by weight, preferably 0.001 to 0.05% by weight, in terms of a metalatom in the polycondensation catalyst (1) or (2), based on the weight ofa mixture of the aromatic dicarboxylic acid and the aliphatic dial. Whenthe amount of the hydrolyzate (I-m) or (I-n) is within the above range,the effect of shortening the polycondensation time is high.

The hydrolyzate (I-m) or (I-n) can be fed to the reactor in theesterification reaction step, or can be fed to the reactor in the firststage of the liquid phase polycondensation reaction step.

When the co-catalyst component (IIa) is added, this component isdesirably used in such an amount that the molar ratio ((M)/(I-m)) of themetal atom (M) in the co-catalyst component to titanium in thehydrolyzate (I-m) or the molar ratio ((M)/(I-n)) of the metal atom (M)in the co-catalyst component to titanium and another element in thehydrolyzate (I-n) is in the range of 1/50 to 50/1, preferably 1/40 to40/1, more preferably 1/30 to 30/1. When a phosphorus compound such as aphosphate or a phosphite is used, the amount thereof is an amount interms of a metal atom contained in the phosphoruos compound.

The co-catalyst component (IIa) can be fed to the reactor in theesterification reaction step, or can be fed to the reactor in the firststage of the liquid phase polycondensation reaction step. Further, theco-catalyst component can be added at the same time as the hydrolyzate(I-m) or (I-n) or separately.

The at least one compound selected from cyclic lactone compounds andhindered phenol compounds is used in an amount of usually 10 to 2000ppm, preferably 30 to 1000 ppm, based on aromatic dicarboxylic acidunits in the low condensate. When the amount of at least one compoundselected from cyclic lactone compounds and hindered phenol compounds isin the above range, a polyester having a low content of acetaldehyde canbe obtained.

The at least one compound selected from cyclic lactone compounds andhindered phenol compounds can be fed in the reactor in theesterification reaction step, or can be fed to the reactor in the firststage of the liquid phase polycondensation reaction step. Further, suchcompound can be added at the same time as the hydrolyzate (I-m) or (I-n)or separately.

In the present invention, at least one phosphorus compound selected fromphosphoric acid and phosphoric esters may be used in combination in thepolycondensation reaction. Examples of the phosphoric esters includetrimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctylphosphate, triphenyl phosphate and tricresyl phosphate.

The phosphoric compound is used in an amount of usually 0.001 to 0.1% byweight, preferably 0.002 to 0.02% by weight, in terms of phosphorusatom, based on the weight of a mixture of the aromatic dicarboxylic acidand the aliphatic diol.

The phosphoric compound can be fed to the reactor in the esteriafionreaction step, or can be fed to the reactor in the first stage of theliquid phase polycondensation reaction step.

The polyester obtained by the above process has a low acetaldehydecontent. From such polyester, molded products hardly generating bad odoror foreign odor or hardly changing flavor or scent of the contents canbe obtained.

The acetaldehyde content in the polyester is measured by the aforesaidmethod.

According to the present invention, a polyester can be produced withhigh polymerization activity, and the resulting polyester has a lowacetaldehyde content.

A still further embodiment of the process for producing a polyesteraccording to the invention is described below.

This embodiment is a process for producing a polyester, comprising anesterification step in which an aromatic dicarboxylic acid or anester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof are esterified to form a low condensateand a polycondensation step in which the low condensate is polycondensedin the presence of a polycondensation catalyst to increase the molecularweight, wherein:

-   -   the polycondensation catalyst used is a catalyst comprising:        -   (II) a polycondensation catalyst component comprising a            hydrolyzate (I-m) obtained by hydrolyzing a titanium halide            or a hydrolyzate (I-n) obtained by hydrolyzing a mixture of            a titanium halide and a compound of at least one element            selected from elements other than titanium or a precursor of            the compound, and        -   (II) a co-catalyst component comprising a compound of at            least one element selected from the group consisting of            beryllium, magnesium, calcium, strontium, barium, boron,            aluminum, gallium, manganese, cobalt, zinc, germanium,            antimony and phosphorus; and    -   a tint adjusting agent is added in the esterification step or        the polycondensation step.

The hydrolyzate (I-m) obtained by hydrolyzing a titanium halide and thehydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halideand a compound of at least one element selected from elements other thantitanium or a precursor of the compound are the same as the hydrolyzate(I-m) and the hydrolyzate (I-n) previously described, respectively.

Examples of the co-catalyst components (II) comprising a compound of atleast one element selected from the group consisting of beryllium,magnesium, calcium, strontium, barium, boron, aluminum, gallium,manganese, cobalt, zinc, germanium, antimony and phosphorus include thesame co-catalyst compounds as previously described. Preferred examplesof the co-catalyst components (II) include magnesium compounds such asmagnesium carbonate and magnesium acetate; calcium compounds such ascalcium carbonate and calcium acetate; and zinc compounds such as zincchloride and zinc acetate. The co-catalyst compounds can be used singlyor in combination of two or more kinds.

The production of a polyester comprising an esterification step in whichan aromatic dicarboxylic acid or an ester-forming derivative thereof andan aliphatic diol or an ester-forming derivative thereof are esterifiedto form a low condensate and a polycondensation step in which the lowcondensate is polycondensed in the presence of a polycondensationcatalyst to increase the molecular weight is carried out through theesterification step, the liquid phase polycondensation step, and ifnecessary, the solid phase polycondensation step, as described above.

The polycondensation catalyst component (I) is used in an amount ofusually 0.0005 to 0.2% by weight, preferably 0.001 to 0.05% by weight,in terms of weight of a metal in the catalyst component (I), based onthe weight of a mixture of the aromatic dicarboxylic acid and thealiphatic diol.

The co-catalyst component (II) is desirably used in such an amount thatthe molar ratio ((M)/(Ti)) of the metal atom (M) in the co-catalystcomponent to titanium (and another element if the component (I) containsanother element) (TI) in the polycondensation catalyst component (I) isin the range of 1/50 to 50/1, preferably 1/40 to 40/1, more preferably1/30 to 30/1. When a phosphorus compound such as a phosphate or aphosphite is used as the co-catalyst component, the amount thereof is anamount in terms of a metal atom contained in the phosphorus compound.

The co-catalyst component (II) can be fed to the polymerization reactorin the esterification reaction step, or can be fed to the reactor in thefirst stage of the liquid phase polycondensation reaction step. Further,the co-catalyst component can be added at the same time as thepolycondensation catalyst component or separately.

The tint adjusting agent employable herein is, for example, an organicpigment, an inorganic pigment, an organic dye or an inorganic dye, andis particularly preferably one having a tint of blue or red. Specificexamples thereof include Solvent Blue 104, Pigment Red 263, Solvent Red135, Pigment Blue 29, Pigment Blue 15:1, Pigment Blue 15:3, Pigment Red187 and Pigment Violet 19 (Color Index Name).

The tint adjusting agents can be used singly or in combination.

The tint adjusting agent is used in an amount of usually 0.05 to 100ppm, preferably 0.1 to 50 ppm, based on the weight of the polyester.

The tint adjusting agent can be fed to the reactor in the esterificationreaction step, or can be fed to the reactor in the first stage of theliquid phase polycondensation reaction step. Further, the tint adjustingagent can be added at the same time as the polycondensation catalystcomponent or separately.

According to the present invention, a polyester having a good tint canbe produced with high polymerization activity.

Next, the method for treating a polyester according to the presentinvention is described.

One embodiment of the method for treating a polyester according to theinvention comprises bringing a polyester, which is obtained by the useof titanium compound catalyst and in which the reaction has beencompleted, into contact with a phosphorous acid aqueous solution, ahypophosphorous acid aqueous solution, a phosphoric ester aqueoussolution, a phosphorous ester aqueous solution or a hypophosphorousester aqueous solution, each of said solutions having a concentration ofnot less than 10 ppm in terms of phosphorus atom.

Another embodiment of the method for treating a polyester according tothe invention comprises bringing a polyester, which is obtained by theuse of a titanium compound catalyst and in which the reaction has beencompleted, into contact with an organic solvent

A further embodiment of the method for treating a polyester according tothe invention comprises bringing a polyester, which is obtained by theuse of a titanium compound catalyst and in which the reaction has beencompleted, into contact with an organic solvent solution of phosphoricacid, an organic solvent solution of a phosphoric ester, and organicsolvent solution of phosphorous acid, an organic solvent solution ofhypophosphorous acid, an organic solvent solution of a phosphorous esteror an organic solvent solution of a hypophosphorous ester, each of saidsolutions having a concentration of not less than 10 ppm in terms ofphosphorus atom.

The polyester used in the treating method of the invention is apolyester produced by using as starting materials an aromaticdicarboxylic acid or an ester-forming derivative thereof, an aliphaticdiol or an ester-forming derivative thereof, and if necessary, apolyfunctional compound or the like, and is preferably polyethyleneterephthalate produced by using as starting materials terephthalic acidor an ester-forming derivative thereof and ethylene glycol or anester-forming derivative thereof. In the polyethylene terephthalate,other dicarboxylic acids and/or other glycols may be copolycondensed inamounts of not more than 20% by mol.

Examples of dicarboxylic acids other than terephthalic acid includearomatic dicarboxylic acids, such as phthalic acids, isophthalic acid,naphthalenedicarboxylic acid, diphenyldicarboxylic acid anddiphenoxyethanedicarboxylic acid; aliphatic dicarboxylic acids, such asadipic acid, sebacic acid, azelaic acid and decanedicarboxylic acid;alicyclic dicarboxylic acids, such as cyclohexanedicarboxylic acid; andester-forming derivatives thereof.

Examples of glycols other than ethylene glycol include aliphaticglycols, such as trimethylene glycol, propylene glycol, tetramethyleneglycol, neopentyl glycol, hexamethylene glycol and dodecamethyleneglycol; alicyclic glycols, such as cyclohexanedimethanol; aromaticdiols, such as bisphenols, hydroquinone,2,2-bis(4-β-hydroxyethoxyphenyl)propane, 1,3-bis(2-hydroxyethoxy)benzeneand 1,4-bis(2-hydroyethoxy)benzene; and ester-forming derivativesthereof

The polyester used in the treating method of the invention can beproduced by using, as starting materials, the aromatic dicarboxylic acidor an ester-forming derivative thereof and the aliphatic diol or anester-forming derivative thereof, preferably terephthalic acid or anester-forming derivative thereof and ethylene glycol or an ester-formingderivative thereof, and performing the esterification, the liquid phasepolycondensation, and if necessary, the solid phase polycondensation, aspreviously described.

The polycondensation reaction is preferably carried out in the presenceof the below-described polycondensation catalyst and the aforesaidstabilizer.

The polycondensation catalyst employable herein is, for example, theaforesaid hydrolyzate (I-m) obtained by hydrolyzing a titanium halide orthe aforesaid hydrolyzate (I-n) obtained by hydrolyzing a mixture of atitanium halide and a compound of at least one element selected fromelements other than titanium or a precursor of the compound.

Also employable as the polycondensation catalyst are titanium alkoxide,such as titanium butoxide and titanium tetraisopropoxide; organictitanium compounds, such as an acetylacetonato salt of titanium; andtitanium compounds, such as a hydrolyzate obtained by hydrolyzingtitanium alkoxide. The hydrolyzate of titanium alkoxide can be preparedin a manner similar to that for preparing the hydrolyzate of titaniumhalide previously described.

The hydrolyzate (I-m) or the hydrolyzate (I-n) (titanium-containinghydrolyzate (A-2)) isused in combination with a co-catalyst component(II), if desired.

Examples of the co-catalyst components (II) include the same co-catalystcompounds previously described. Of these, preferable are magnesiumcompounds, such as magnesium carbonate and magnesium acetate; calciumcompounds, such as calcium carbonate and calcium acetate; and zinccompounds such as zinc chloride and zinc acetate. The co-catalystcompounds can be used singly or in combination of two or more kinds.

When the magnesium compound is used as the co-catalyst component, apolyester (particularly, polyethylene terephthalate) having excellenttransparency can be obtained.

The co-catalyst component (II) is desirably used in such an amount thatthe molar ratio ((II)/(A-2)) of the metal atom in the co-catalystcomponent (II) to titanium (and another element if thetitanium-containing hydrolyzate (A-2) contains another element) in thetitanium-containing hydrolyzate (A-2) is in the range of 1/50 to 50/1,preferably 1/40 to 40/1, more preferably 1/30 to 30/1. When a phosphoruscompound such as a phosphate or a phosphite is used, the amount thereofis an amount in terms of a metal atom contained in the phosphoruscompound.

The polycondensation catalyst (II) is used in an amount of usually0.0005 to 0.2% by weight, preferably 0.001 to 0.05% by weight, in termsof weight of a metal in the polycondensation catalyst, based on theweight of a mixture of the aromatic dicarboxylic acid and the aliphaticdiol. The stabilizer is used in an amount of usually 0.001 to 0.1% byweight, preferably 0.002 to 0.02% by weight, in terms of phosphorus atomin the stabilizer. The polycondensation catalyst and the stabilizer canbe fed to the reactor in the liquid phase esterification reaction step,or can be fed to the reactor in the first stage of the polycondensationreaction step.

When the polyester of the invention is polyethylene terephthalate, thepolyethylene terephthalate obtained from the last polycondensationreactor in the polycondensation reaction step desirably comprises:

-   -   95.0 to 99.0% by mol of ethylene terephthalate component units        represented by the following formula:

and

-   -   1.0 to 5.0%by mol of dioxyethylene terephthalate component units        represented by the following formula:

The intrinsic viscosity of the polyester obtained as above is desired tobe usually not less than 0.50 dl/g, preferably 0.50 to 1.50 dl/g, morepreferably 0.72 to 1.0 dl/g. The density of the polyester is desired tobe usually not less than 1.37 g/cm³, preferably 1.37 to 1.44 g/cm³, morepreferably 1.38 to 1.43 g/cm³, still more preferably 1.39 to 1.42 g/cm³.

The acetaldehyde content in the polyester is desired to be not more than5 ppm, preferably 0 to 3 ppm, particularly preferably 0 to 2 ppm. Theacetaldehyde content is measured by the aforesaid method.

In the method for treating a polyester according to the invention, apolyester in which the reaction of the polyester production has beencompleted is used. The “polyester in which the reaction has beencompleted” means a polyester which does not exhibit a further increaseof its viscosity after the reaction, and is for example a polyestergiven after the liquid phase polycondensation step or a polyester givenafter the solid phase polycondensation step. The polyester is usuallyparticulate, but it may be in the form of powder or strand.

In the present invention, the polyester, preferably polyethyleneterephthalate, is subjected to:

-   -   a phosphorous-containing aqueous solution treatment in which the        polyester, preferably polyethylene terephthalate, is brought        into contact with a phosphorous acid aqueous solution, a        hypophosphorous acid aqueous solution, a phosphoric ester        aqueous solution, a phosphorous ester aqueous solution or a        hypophosphorous ester aqueous solution (each solution sometimes        being referred to as a “phosphorus-containing aqueous solution”        hereinafter);    -   an organic solvent treatment in which the polyester, preferably        polyethylene terephthalate, is brought into contact with an        organic solvent; or    -   a phosphorous-containing organic solvent solution treatment in        which the polyester, preferably polyethylene terephthalate, is        brought into contact with an organic solvent solution of        phosphoric acid, an organic solvent solution of phosphoric acid,        an organic solvent solution of hypophosphorous acid, an organic        solvent solution of a phosphoric ester, an organic solvent        solution of a phosphorous ester or an organic solvent solution        of a hypophosphorous ester (each solution sometimes being        referred to as a “phosphorus-containing organic: so,vent        solution” hereinafter).

Examples of the phosphoric esters used in the phosphorus-containingaqueous solution treatment include monomethyl phosphate, dimethylphosphate, trimethyl phosphate, monomethyl phosphate, diethyl phosphate,triethyl phosphate, tributyl phosphate, tri-n-butyl phosphate, trioctylphosphate, triphenyl phosphate and tricresyl phosphate. Examples of thephosphorous eaters include methyl phosphite, dimethyl phosphite,trimethyl phosphite, ethyl phosphite, diethyl phosphite, triethylphosphite, tributyl phosphite, triphenyl phosphite, trisdodecylphosphite and trisnonylphenyl phosphite. Examples of the hypophosphorousesters include methyl hypophosphite and trimethyl hyophosphite.

The phosphorus-containing aqueous solution to be contacted with thepolyester desirably has a concentration (in terms of phosphorus atom) ofnot less than 10 ppm, preferably 10 to 100000 ppm, more preferably 100to 70000 ppm, particularly preferably 1000 to 50000 ppm.

When the concentration of the phosphorus-containing aqueous solution isin the above range, the effect of inhibiting increase of theacetaldehyde content is high in the molding of the resulting polyester,and the molding can be made economically.

The contact of the polyester with the phosphorus-containing aqueoussolution car be carried out continuously or batchwise.

In the batchwise contact of the polyester with the phosphorus-containingaqueous solution, for example, a silo type treating apparatus isemployable. In detail, the polyester and the phosphorus-containingaqueous solution are introduced into a silo to immerse the polyester inthe phosphorus-containing aqueous solution. It is also possible that thepolyester and the phosphorus-containing aqueous solution are introducedinto a rotary cylindrical container to immerse the polyester in thephosphorus-containing aqueous solution and contacted while rotating thecylindrical container to perform the contact more efficiently.

In the continuous contact of the polyester with thephosphorus-containing aqueous solution, for example, a tower typetreating apparatus is employable. The polyester is continuously fed tothe tower type treating apparatus at its top, and thephosphorus-containing aqueous solution is continuously fed to theapparatus as a counter flow or a parallel flow, whereby the polyester isimmersed in the phosphorus-containing aqueous solution to contact themwith each other.

The temperature for the contact of the polyester with thephosphorus-containing aqueous solution is in the range of usually 0 to100° C., preferably 10 to 95° C., and the contact time is in the rangeof usually 5 minutes to 10 hours, preferably 30 minutes to 6 hours.

After the contact of the polyester with the phosphorous-containingaqueous solution, the polyester is separated from thephosphorus-containing aqueous solution, hydro-extracted by ahydro-extracting device such as a particle vibrating screen or a SimonCarter (Gel dryer), and dried. Drying of the polyester having beencontacted with the phosphorus-containing aqueous solution can be carriedout by a conventional drying method.

In order to continuously dry the polyester, a hopper type through-flowdryer in which the polyester is fed at the top and a drying gas is fedfrom the bottom and passed through is generally used. For decreasing thedrying gas and thereby efficiently drying the polyester, a method ofusing a continuous dryer of rotary disc heating type is available. Inthis method, while passing a small amount of a drying gas, a heatingsteam or a heating medium is fed to a rotary disc or an external jacketto indirectly heat and dry the polyester.

In order to batchwise dry the polyester, a method of using a double-conetype rotary dryer is available. In this method, the polyester is driedunder reduced pressure, or under reduced pressure with passing a smallamount of a drying gas, or at atmospheric pressure with passing a dryinggas. The drying gas may be the atmosphere, but dry nitrogen ordehumidified air is preferable from the viewpoint of inhibition ofdecrease of the molecular weight due to the hydrolysis of the polyester.

When the polyester is brought into contact with thephosphorus-containing aqueous solution as described above, the resultingpolyester has small increase of the acetaldehyde content and smalldecrease of the intrinsic viscosity in the molding process. The reasonis presumably that the polycondensation catalyst in the polyester isdeactivated by the contact of the polyester with thephosphorous-containing aqueous solution.

From such polyester, molded products hardly generating bad odor orforeign odor or hardly changing flavor or scene of the contents can beobtained.

This can be confirmed by, for example, measuring increase of theacetaldehyde content after the polyester is heated to a temperature of275° C. to melt it and then molded into a stepped square plate moldedproduct. The steeped square plate molded product can be produced in thefollowing manner.

In the first place, 2 kg of a particulate polyester (i.e., polyesterpellets, starting material) whose acetaldehyde content (x % by weight)has been beforehand measured is dried for 16 hours or more under theconditions of a temperature of 140° C. and a pressure of 10 Torr using atray dryer, to allow the particulate polyester to have a water contentof not more than 50 ppm.

The particulate polyester thus dried is then injection molded by aninjection molding machine of M-70A manufactured by Meiki Seisakusho K.K.to obtain a stepped square plate molded product. In the molding,nitrogen having a dew point of −70° C. is fed to the upper part of thehopper and the screw feeder shooting part at a rate of 5 Nm³/hr. Themolding is carried out under the conditions of a barrel presettemperature of 275° C., C1/C2/C3/ nozzle tip temperatures of the moldingmachine of 260° C./290° C./290° C./300° C., and a mold coolingtemperature of 15° C.

In the injection molding, the dried particulate polyester is fed throughthe hopper to the injection molding machine having been adjusted to havemolding conditions of metering of 12 seconds and injection of 60seconds. The residence time of the molten resin in the molding machineis about 72 seconds. The weight of a stepped square plate molded productis 75 g, and any one of the eleventh to fifteenth stepped square platemolded products from the beginning of the injection molding is used as aspecimen for measuring the acetaldehyde content.

The stepped square plate molded product has a shape shown in FIG. 1, andthe thicknesses of the parts A, B and C are about 6.5 mm, about 5 mm andabout 4 mm, respectively. The acetaldehyde content in the molded productis measured using the part C.

The part C of the stepped square plate molded product produced as aboveis cut into chips, and using the chips as acetaldehyde content measuringsamples, the acetaldehyde content is measured.

When the polyester, preferably polyethylene terephthalate, is subjectedto the phosphorus-containing aqueous solution treatment as describedabove, the resulting polyester has small increase of the acetaldehydecontent and small decrease of the intrinsic viscosity in the moldingprocess.

The organic solvent treatment is described below.

Examples of organic solvent used in the organic solvent treatmentinclude alcohols having 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, such as methanol, ethanol, propanol, isopropanol, butanol,pentanol, hexanol, 2-ethylhexanol, octanol, dodecanol, octadecylalcohol, oleyl alcohol, benzyl alcohol, phenylethyl alcohol, cumylalcohol, isopropyl alcohol and isopropylbenzyl alcohol; ketones having 3to 15 carbon atoms, preferably 3 to 9 carbon atoms, such as acetone,methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenoneand benzoquinone; and saturated hydrocarbons having 5 to 16 carbonatoms, preferably 5 to 10 carbon atoms, such as butane, pentane, hexane,heptane, octane, nonane, decane, undecane, dedocena, tridecane,tetradecane, pentadecane and hexadecane. Of theses, isopropanol oracetone is preferable.

The contact of the polyester with the organic solvent can be carried outcontinuously or batchwise. Specifically, the contact can be carried outin the same manner as in the phosphorus-containing aqueous solutiontreatment except for using the organic solvent instead of thephosphorus-containing aqueous solution.

The temperature for the contact of the polyester with the organicsolvent is in the range of usually 0 to 100° C., preferably 10 to 95°C., although it varies depending upon the boiling point of the organicsolvent. The contact time is in the range of usually 3 minutes to 5hours, preferably 30 minutes to 4 hours.

After the contact of the polyester with the organic solvent, thepolyester is separated from the organic solvent, hydro-extracted by ahydro-extracting device such as a particle vibrating screen or a SimonCarter (Gel dryer), and dried. Drying of the polyester having beencontacted with the organic solvent can be carried out by a conventionaldrying method. Specifically, the continuous drying method or thebatchwise drying method described above is available.

When the polyester is brought into contact with the organic solvent asdescribed above, the resulting polyester has small increase of theacetaldehyde content during the molding process. The reason ispresumably that the polycondensation catalyst in the polyester isdeactivated by the contact of the polyester with the organic solvent.

Form such polyester, molded products hardly generating bad odor orforeign odor or hardly changing flavor or scent of the contents can beobtained. This can be confirmed by measuring the acetaldehyde content inthe sample, which is obtained by heating the polyester to a temperatureof 270° C. to melt it and then cooling it to room temperature, inaccordance with the aforesaid method.

When the polyester, preferably polyethylene terephthalate, is subjectedto the organic solvent treatment as described above, the resultingpolyester has small increase of the acetaldehyde content during themolding process.

The phosphorous-containing organic solvent solution treatment isdescribed below.

Examples of phosphoric esters used in the phosphorus-containing organicsolvent solution treatment include the same phosphoric esters as used inthe phosphorus-containing aqueous solution treatment.

Examples of organic solvents used in the phosphorus-containing organicsolvent solution treatment include the same organic solvent as used inthe organic solvent treatment. Of these, isopropanol or acetone ispreferable.

The phosphorus-containing organic solvent solution to be contacted withthe polyester has a concentration (in terms of phosphorus atom) of notless than 10 ppm, preferably 10 to 100000 ppm, more preferably 100 to70000 ppm, particularly preferably 1000 to 50000 ppm.

When the concentration of the phosphorus-containing organic solventsolution is in the above range, the effect of inhibiting increase of theacetaldehyde content is high in the molding of the resulting polyester,and the molding can be made economically.

The contact of the polyester with the phosphorus-containing organicsolvent solution can be carried out continuously or batchwise.Specifically, the contact can be carried out in the same manner as inthe phosphorous-containing aqueous solution treatment except for usingthe phosphorous-containing organic solvent solution instead of thephosphorus-containing aqueous solution.

The temperature for the contact of the polyester with thephosphorus-containing organic solvent solution is in the range ofusually 0 to 100° C., preferably 0 to 95° C., although it variesdepending upon the boiling point of the organic solvent. The contacttime is in the range of usually 5 minutes to 10 hours, preferably 30minutes to 6 hours.

After the contact of the polyester with the phosphorus-containingorganic solvent solution, the polyester is separated from thephosphorus-containing organic solvent solution, hydro-extracted by aparticle hydro-extracting device such as a vibrating screen or a SimonCarter and dried. Drying of the polyester having been contacted with thephosphorus-containing organic solvent solution can be carried out by aconventional drying method. Specifically, the continuous drying methodor the batchwise drying method described above is available.

When the polyester is brought into contact with thephosphorus-containing organic solvent solution as described above, theresulting polyester has small increase of the acetaldehyde contentduring the molding process. The reason is presumably that thepolycondensation catalyst in the polyester is deactivated by the contactof the polyester with the phosphorus-containing organic solventsolution.

From such polyester, molded products hardly generating bad odor orforeign odor or hardly changing flavor or scent of the contents can beobtained.

This can be confirmed by measuring the acetaldehyde content in thesample, which is obtained by heating the polyester to a temperature of285° C. to melt it and then cooling it to room temperature, inaccordance with the aforesaid method.

When the polyester, preferably polyethylene terephthalate, is subjectedto the phosphorus-containing organic solvent solution treatment asdescribed above, the resulting polyester has small increase of theacetaldehyde content during the molding process.

Next, the polyester according to the invention is described.

The polyester (P-1) can be produced by the aforesaid process using thecatalyst for polyester production comprising the solid titanium compound(I-c) and the co-catalyst component (II) or the catalyst for polyesterproduction comprising the titanium-containing solid compound (I-d) andif necessary the co-catalyst component (II).

The intrinsic viscosity of the polyester (P-1) is desired to be usuallynot less than 0.50 dl/g, preferably 0.50 to 1.50 dl/g, more preferably0.72 to 1.0 dl/g. The density thereof is desired to be usually not lessthan 1.37 g/cm³, preferably 1.37 to 1.44 g/cm³, more preferably 1.38 to1.43 g/cm², still more preferably 1.39 to 1.42 g/cm³.

The haze of the polyester (P-1) such as polyethylene terephthalate,i.e., haze of a molded product in the form of a plate having a thicknessof 4 mm obtained by molding the polyester at a molding temperature of275° C., is usually not more than 20%, preferably 0 to 10%.

The plate molded product for the measurement of a haze is the part C ofthe aforesaid stepped square plate molded product, and the steppedsquare plate molded product can be produced in the same manner as forthe stepped square plate molded product for the measurement of increaseof the acetaldehyde content. As a specimen for measuring the haze, anyone of the eleventh to fifteenth stepped square plate molded productsfrom the beginning of the injection molding is used. In the measurementof a haze, a haze meter (Suga tester) HGM-2DP is used.

The polyester (P-1) is excellent in tint, partially in transparency, andhas a low acetaldehyde content. The polyester (P-1) can be used as amaterial of various molded products. For example, the polyester is meltmolded and used as blow molded articles (e.g., bottles), sheets, films,fibers, etc., but it is partially preferably used as bottles.

In order to produce bottles, sheets, films, fibers, etc. from thepolyester (P-1) such as polyethylene terephthalate, hitherto knownprocesses are available.

Examples of the processes for producing bottles include a processcomprising extruding the polyester (P-1) (preferably polyethyleneterephthalate) in a molten state from a die to form a tubular parison,holding the parison in a mold of desired shape, and blowing air into theparison to fit it to the mold thereby to produce a blow molded article,and a process comprising injection molding the polyester (P-1)(preferably polyethylene terephthalate) to form a preform, heating thepreform up to a temperature appropriate to stretching, holding thepreform in a mold of desired shape, and blowing air into the preform tofit it to the mold thereby to produce a blow molded article.

One example of the process for producing films or sheets is a processcomprising extruding molten polyethylene terephthalate from a T-dieusing an extruder and molding conditions hitherto known. The thusobtained films and sheets may be stretched by a known stretching method.

One example of the process for producing fibers is a process comprisingextruding a molten polyester (P-1), preferably molten polyethyleneterephthalate, through a spinneret. The thus obtained fibers may bestretched.

The polyester (P-1), preferably polyethylene terephthalate, and themolded products obtained therefrom are excellent in transparency andtint and have a low acetaldehyde content.

Another embodiment of the polyester according to the invention isdescribed below.

The polyester (P-2) is obtained by the aforesaid process for producing apolyester, wherein:

The polycondensation catalyst which comprises the polycondensationcatalyst compound (II) comprising the hydrolyzate (I-m) or thehydrolyzate (I-n) and the co-catalyst component (II) is used, and

a tint adjusting gent is added in the esterification step or thepolycondensation step.

The intrinsic viscosity of the polyester (P-2) is desired to be usuallynot less than 0.50 dl/g, preferably 0.50 to 1.50 dl/g, more preferably0.72 to 1.0 dl/g. The density thereof is desired to be usually not lessthan 1.37 g/cm³, preferably 1.37 to 1.44 g/cm³, more preferably 1.38 to1.43 g/cm³, still more preferably 1.39 to 1.42 g/cm³.

In the polyester (P-2),

-   -   a titanium atom is contained in an amount of 0.1 to 200 ppm,        preferably 0.5 to 100 ppm, more preferably 1 to 50 ppm, based on        the weight of the polyester, and    -   a metal atom M selected from beryllium, magnesium, calcium,        strontium, barium, boron, aluminum, gallium, manganese, cobalt,        zinc and antimony is contained in an amount of 0.1 to 500 ppm,        preferably 0.5 to 300 ppm, more preferably 1 to 250 ppm, based        on the weight of the polyester.

The metal atom M is preferably magnesium, calcium or zinc, particularlypreferably magnesium. Two or ore kinds of metal atoms M may becontained, and in this case, the total of two or more kinds of the metalatoms is within the above range.

The titanium atom contained in the polyester (P-2) is preferably atitanium atom derived from the polycondensation catalyst obtained byhydrolyzing a titanium halide, and the metal atom M is preferably ametal atom derived from the co-catalyst component.

The molar ratio (titanium atom/metal atom M) of the titanium atom to themetal atom M is in the range of 1/50 to 50/1, preferably 1/40 to 40/1,more preferably 1/30 to 30/1.

The titanium atom content and the metal atom content in the polyester ofthe invention is measured by a fluorescent X-ray method.

In the polyester (P-2), the tint adjusting agent is desirably containedin an amount of 0.01 to 100 ppm, preferably 0.1 to 50 ppm.

The content of a germanium atom in the polyester (P-2) is desirably notmore than 5 ppm.

The polyester (P-2), preferably polyethylene terephthalate, has anexcellent tint.

A further embodiment of the polyester according to the invention isdescribed below.

The intrinsic viscosity of the polyester (P-3) is desired to be usuallynot less than 0.50 dl/g, preferably 0.50 to 1.50 dl/g, more preferably0.72 to 1.0 dl/g. The density thereof is desired to be usually not lessthan 1.37 g/cm³, preferably 1.37 to 1.44 g/cm³, more preferably 1.38 to1.43 g/cm³, still more preferably 1.39 to 1.42 g/cm³.

In the polyester (P-3),

-   -   a titanium atom is contained in an amount of 0.1 to 200 ppm,        preferably 0.5 to 100 ppm, more preferably 1 to 50 ppm, based on        the weight of the polyester, and    -   a metal atom M selected from beryllium, magnesium, calcium,        strontium, barium, boron, aluminum, gallium, manganese, cobalt,        zinc and antimony is contained in an amount of 0.1 to 500 ppm,        preferably 0.5 to 300 ppm, more preferably 1 to 250 ppm, based        on the weight of the polyester.

The metal atom M is preferably magnesium, calcium or zinc, particularlypreferably magnesium. Two or more kinds of metal atoms M may becontained, and in this case, the total of two or more kinds of the metaltoms is within the above range.

The content of a germanium atom in the polyester (P-3) is desirably notmore than 5 ppm.

The titanium atom contained in the polyester (P-3) is preferably atitanium atom derived from the polycondensation catalyst obtained byhydrolyzing a titanium halide, and the metal atom M is preferably ametal atom derived from the co-catalyst component.

The molar ratio (titanium atom/metal atom M) of the titanium atom to themetal atom M is in the range of usually 0.05 to 50, preferably 0.1 to30, more preferably 0.2 to 25.

In the polyester (P-3), the content (W₀ ppm) of acetaldehyde is not morethan 4 ppm, preferably 0.1 to 3.5 ppm, more preferably 0.5 to 3.0 ppm.

When a content of acetaldehyde in a stepped square plate molded productobtained by heating the polyester (P-3) (acetaldehyde content: W₀ ppm)to a temperature of 275° C. to melt it and molding the molten polyesteris taken as W₁ ppm, the value of W₁−W₀ is not more than 10 ppm,preferably not more than 9 ppm.

The polyester (P-3), preferably polyethylene terephthalate, has a lowacetaldehyde content and is remarkably inhibited in increase of theacetaldehyde content when the polyester is molded into a molded product.For example, when the polyester (P-3) is molded into a bottle, flavor orscent of the contends filled in the bottle is hardly deteriorated.

In the present invention, the increase of the acetaldehyde contentduring the molding is determined by measuring an acetaldehyde content ina stepped square plate molded product of the polyester by the aforesaidmethod.

In the present invention, the term “acetaldehyde content” means anacetaldehyde content (W₀ ppm) measured with respect to the polyesterbefore molding and an acetaldehyde content (W₁ ppm) measured withrespect to the molded product obtained by injection molding of thepolyester at a molding temperature of 275° C. From the values of W₀ ppmand W₁ ppm, a value of W₁−W₀ is calculated.

When a polyester having a low acetaldehyde content (W₀ ppm) and a W₁−W₀value (i.e., increase of acetaldehyde) of not more than 10 ppm is used,a molded product hardly generating bad odor or foreign odor and hardlychanging flavor or scent of the contents can be obtained because theacetaldehyde content in the molded product is low.

The polyester (P-3) is preferably polyethylene terephthalate.

The polyester (P-3) having the above properties is obtained by preparinga polyester in a manner similar to that for preparing a polyester usedin the aforesaid polyester treating method and then subjecting thepolyester in which the reaction has been completed to thephosphorus-containing aqueous solution treatment, the organic solventtreatment or the phosphorus-containing organic solvent solutiontreatment.

The acetaldehyde content in the polyester to be subjected to thephosphorus-containing aqueous solution treatment, the organic solventtreatment or the phosphorus-containing organic solvent solutiontreatment is usually not more than 4 ppm, preferably 0.1 to 3.5 ppm,more preferably 0.5 to 3.0 ppm.

Of the above treatments, the phosphorus-containing aqueous solutiontreatment and the phosphorus-containing organic solvent solutiontreatment are preferable, and the phosphorus-containing aqueous solutiontreatment is more preferable.

By subjecting the polyester in which the reaction as been completed tothe phosphorus-containing aqueous solution treatment, the organicsolvent treatment or the phosphorus-containing organic solvent solutiontreatment, increase of the acetaldehyde content in the molding processcan be inhibited. The reason why the increase of the acetaldehydecontent in the polyester during the molding can be inhibited bysubjecting the polyester to any of the above treatments is presumablythat the polycondensation catalyst in the polyester is deactivated, andtherefore even when the polyester is heated, the decomposition reactionor the ester interchange reaction hardly proceeds and the amount of theacetaldehyde produced becomes small.

The polyester having been treated as above is remarkably inhibited inthe increase of the acetaldehyde content during the molding process.This can be confirmed by measuring the acetaldehyde content after thepolyester having been subjected to the above treatment is heated to atemperature of 275° C. to melt it and molded into a stepped square platemolded product.

The polyester (P-3) has a low acetaldehyde content and small increase ofacetaldehyde content in the molding process. Therefore, molded products,e.g., bottles, films and sheets, having a low acetaldehyde content canbe obtained from the polyester. If molded products having a highacetaldehyde content are used as containers of foods and drinks, badodor or foreign odor is generated, or flavor or scent of the contents ischanged. Further, photographic films produced from a polyester having ahigh acetaldehyde content are liable to have fog.

The polyester (P-3), preferably polyethylene terephthalate, has a lowacetaldehyde content, and the amount of acetaldehyde produced in themolding process is small. Therefore, the amount of acetaldehydecontained in the resulting molded product is small. Accordingly, whenthe polyester (P-3) is used as a material of bottles, films and sheetsand molded into containers of foods and drinks, flavor or scent of thecontents filled therein is not marred.

A still further embodiment of the polyester according to the inventionis described below.

The intrinsic viscosity of the polyester (P-4) is desired to be usuallynot less than 0.50 dl/g, preferably 0.50 to 1.50 dl/g, more preferably0.72 to 0.1 dl/g. The density thereof is desired to be usually not lessthan 1.37 g/cm³, preferably 1.37 to 1.44 g/cm³, more preferably 1.38 to1.43 g/cm³, still more preferably 1.39 to 1.42 g/cm³.

In the polyester (P-4),

-   -   a titanium atom is contained in an amount of 0.1 to 200 ppm,        preferably 0.5 to 100 ppm, more preferably 1 to 50 ppm, based on        the weight of the polyester, and    -   a metal atom M selected from beryllium, magnesium, calcium,        strontium, barium, boron, aluminum, gallium, manganese, cobalt,        zinc and antimony is contained in an amount of 0.1 to 500 ppm,        preferably 0.5 to 300 ppm, more preferably 1 to 250 ppm, based        on the weight of the polyester.

The metal atom M is preferably magnesium, calcium or zinc, particularlypreferably magnesium. Two or more kinds of metal atoms M may becontained, and in this case, the total to two or more kinds of the metalatoms is within the above range.

The content of a germanium atom in the polyester (P-4) is desirably notmore than 5 ppm.

The titanium atom contained in the polyester (P-4) is preferably atitanium atom derived from the polycondensation catalyst obtained byhydrolyzing a titanium halide, and the metal atom M is preferably ametal atom derived from the co-catalyst component.

The molar ratio (titanium atom/metal atom M) of the titanium atom to themetal atom M is in the range of usually 0.05 to 50, preferably 0.1 to30, more preferably 0.2 to 25.

In the polyester (P-4), the content (x % by weight) of a cyclic trimer(cyclic trimer of ethylene terephthalate represented by the followingformula) is not more than 5% by weight, preferably not more than 0.45%by weight.

When a content of a cyclic trimer is a stepped square plate moldedproduct obtained by heating the polyester (P-4) (content of cyclictrimer: x % by weight) to a temperature of 290° C. to melt it andmolding the molten polyester is taken as y % by weight, x and ydesirably satisfy the following relation

-   -   y≦−0.20x+0.20,    -   preferably y≦−0.20x+0.18,    -   more preferably y≦−0.20x+0.16.

The polyester (P-4) has a low cyclic trimer content. Further, increaseof the cyclic trimer content is remarkably inhibited when the polyesteris molded into a molded product, and the amount of a cyclic trimercontained in the polyester is small in the molding process, so thatstain of a mold hardly takes place. For example, in the production of ablow molded article comprising feeding the polyester (P-4) to a moldingmachine such as an injection molding machine to prepare a preform for ablow molded article, inserting the preform into a mold of given shapeand conducting stretch blow molding and heat setting, the amount of thecyclic trimer hardly increases, and the amount of the cyclic trimercontained in the polyester in the molding is small, so that stain of themold hardly takes place.

The increase of the cyclic trimer content during the molding of thepolyester (P-4) is determined by measuring the amount of the cyclictrimer contained in a stepped square plate molded product produced fromthe polyester (P-4). The stepped square plate molded product is producedusing, as a starting material, a particulate polyester (P-4) (polyesterpellets) whose cyclic trimer content (x % by weight) has been previouslymeasured, in the same manner as for a stepped square plate moldedproduct used for measuring increase of the acetaldehyde content.

As a specimen for measuring the cyclic trimer content, any one of theeleventh to fifteenth stepped square plate molded products from thebeginning of the injection molding is used. The part C of the steppedsquare plate molded product is cut into chips, and using the chips ascyclic trimer content measuring samples, the cyclic trimer content (z %by weight) is measured.

The cyclic trimer content in the particulate polyester before productionof the stepped square plated molded product and that in the steppedsquare plate molded product are measured in the following manner.

A given amount of a polyester is dissolved in o-chlorophenol, thenreprecipitated with tetrahydrofuran and filtered to remove a linearpolyester. Then, the filtrate is fed to a liquid chromatography (LC7A,manufactured by Shimadzu Seisakusho K.K.) to determine the amount of thecyclic trimer obtained in the polyester. The obtained value is dividedby the amount of the polyester to obtained the cyclic trimer content inthe polyester.

The increase (y % by weight) of the cyclic trimer content given afterthe stepped square plate molded product is produced by melting thepolyester under heating at 290° C. is a value of z (% by weight)−x (% byweight).

The polyester (P-4) is preferably polyethylene terephthalate.

The polyester (P-4) having the above properties is obtained bysubjecting a polyester, which has been produced in a manner similar tothat for preparing a polyester used in the aforesaid polyester treatingmethod and has been obtained through the esterification step, the liquidphase polycondensation step and the solid phase polycondensation step,to the phosphorus-containing aqueous solution treatment, the organicsolvent treatment of the phosphorus-containing organic solvent solutiontreatment. The polyester to be subjected to any of the above treatmentsis usually particulate, but it may be in the form of powder or strand.

The cyclic trimer content in the polyester to be subjected to thephosphorus-containing aqueous solution treatment, the organic solventtreatment or the phosphorus-containing organic solvent solutiontreatment is usually not more than 0.5% by weight, preferably not morethan 0.45% by weight.

The polyester (P-4) having been treated as above is remarkably inhibitedin the increase of the cyclic trimer content when it is molded into ablow molded article or the like. This can be confirmed by measuring thecyclic trimer content after the polyester (P-4) having been subjected tothe above treatment is heated to a temperature of 290° C. to melt it andmolded into a stepped square plate molded product.

By subjecting the polyester to the phosphorus-containing aqueoussolution treatment, the organic solvent treatment or thephosphorus-containing organic solvent solution treatment, increase ofthe cyclic trimer content in the polyester during molding of thepolyester into a stepped square plate molded product under heating to atemperature of 290° C. can be inhibited.

The reason why the increase of the cyclic trimer content in thepolyester during the molding can be inhibited by subjecting thepolyester to the phosphorus-containing aqueous solution treatment, theorganic solvent treatment or the phosphorus-containing organic solventsolution treatment is presumably that the polycondensation catalyst,e.g., titanium compound polycondensation catalyst, in the polyester isdeactivated by any of the above treatments, and therefore even when thepolyester is heated, the decomposition reaction or the ester interchangereaction hardly proceeds and the amount of the cyclic trimer producedbecomes small.

When a molded product is produced from the thus treated polyester (P-4)having a low cyclic trimer content by for example injection molding, theamount of the cyclic trimer contained in the polyester is small in themolding process. Therefore, stain of a mold caused by adhesion of thecyclic trimer to an inner surface of a mold or to a gas exhaust vent ora gas exhaust pipe of a mold hardly takes place, and the cyclic trimerdoes not adhere to a vent zone of an injection molding machine.

The blow molded article according to the invention is produced from thepolyester (P-4) (preferably polyethylene terephthalate) having anintrinsic viscosity of not less than 0.50 dl/g, a titanium atom contentin a specific range, a content of metal atom M in a specific range, atitanium atom/metal atom ratio in a specific range, a cyclic trimercontent of not more than 0.5% by weight and a specific relation betweenthe cyclic trimer content and increase of the cyclic trimer contentafter molding of the polyester into a stepped square plate moldedproduct. This blow molded article has a cyclic trimer content of notmore than 0.6% by weight, preferably 0.10 to 0.55% by weight, morepreferably 0.15 to 0.50% by weight.

Measurement of the cyclic trimer content in the blow molded article iscarried out by the aforesaid method using a sample picked from the blowmolded article.

The blow molded article can be produced by a process hitherto known.Specifically, a preform is first prepared from the polyester (P-4),preferably polyethylene terephthalate. The preform can be prepared by amethod hitherto known, for example, injection molding or extrusionmolding. In the preparation of a preform, the heating temperature ofpolyethylene terephthalate is preferably in the range of 90° C. to 110°C. Then, the preform is heated to a temperature appropriate tostretching and subjected to stretch blow molding to produce a blowmolded article.

If a blow molded article is produced from the polyester (P-4) having alow cyclic trimer content and having been subjected to the specifictreatment, the amount of the cyclic trimer produced in the moldingprocess is small. Therefore, in the production of a low molded articlecomprising feeding the polyester (P-4) to a molding machine such as aninjection molding machine to prepare a blow molded article preform,inserting the preform into a mold of given shape and conducting stretchblow molding and heat setting, stain of a mold caused by adhesion of thecyclic trimer to the mold hardly takes place.

Since the blow molded article according to the invention is obtainedfrom the polyester (P-4) having a low cyclic trimer content and havingbeen subjected to the specific treatment, the amount of a cyclic trimerproduced in the molding process is small, and therefore the blow moldedarticle has a low cyclic trimer content and hardly suffers surfaceroughening or whitening (staining).

In the polyester (P-4), preferably polyethylene terephthalate, thecyclic trimer content is low, and the amount of a cyclic trimer producedin the molding process is small. Therefore, the amount of a cyclictrimer contained in the polyester during the molding is small, and satinof a mold hardly takes place. Accordingly, it is unnecessary to carryout frequent washing in a production of molded products, and hence theproductivity of blow molded articles such as bottles or molded productssuch as films and sheets can be increased. In addition, whitening(staining) of the blow molded articles, films and sheets can beprevented.

The blow molded article according to the invention is obtained from theabove-mentioned polyester, preferably polyethylene terephthalate, sothat the cyclic trimer content in the blow molded article is low, andthe blow molded article hardly suffers surface roughening or whitening(staining).

A still further embodiment of the polyester according to the inventionis described.

The polyester (P-5) is prepared by the use of an aromatic dicarboxylicacid or an ester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof, if necessary, polyfunctional compoundas starting materials, and is preferably polyethylene terephthalatecomprising recurring units dried from terephthalic acid or anester-forming derivative thereof and recurring units derived fromethylene glycol or an ester-forming derivative thereof. The polyethyleneterephthalate may further contain recurring units derived from otherdicarboxylic acids and/or other diols in amounts of not more than 20% bymol.

Examples of dicarboxylic acids other than terephthalic acid and diolsother than ethylene glycol include the same compounds previouslydescribed.

The polyethylene terephthalate may further contain recurring unitsderived from polyfunctional compounds such as trimesic acid,trimethylolethane, trimethylolpropane, trimethylolmethane andpentaerythritol. The recurring units derived from such polyfunctionalcompounds are preferably contained in amounts of 0 to 2% by mol based onthe recurring units derived from diol.

The polyester containing the recurring units derived from thepolyfunctional compounds in the above amount tends to have high meltflowability.

The intrinsic viscosity of the polyester (P-5) is desired to be usuallynot less than 0.50 dl/g, preferably 0.50 to 1.50 dl/g, more preferably0.72 to 1.0 dl/g. The density thereof is desired to be usually not lessthan 1.37 g/cm³, preferably 1.37 to 1.44 g/cm³, more preferably 1.38 to1.43 g/cm³, still more preferably 1.39 to 1.42 g/cm³.

When the ratio (L/T) of a flow length (L) to a flow thickness (T) in theinjection molding of the polyester (P-5) at 290° C. is taken as Y andthe intrinsic viscosity of a molded product obtained by the injectionmolding is taken as X (dl/g), X and Y satisfy the following relationY≧547−500X,preferably Y≧547.5−500X,more preferably Y≧648−500X.

The polyester (P-S), which has the above relation between X and Y withthe proviso that Y is a ratio (L/T) of a flow length (L) to a flowthickness (T) in the injection molding of the polyester at 290° C. and Xis an intrinsic viscosity of a molded product obtained by the injectionmolding, exhibits high melt flowability and excellent moldability evenif the polyester has a high intrinsic viscosity.

In the present invention, the ratio (L/T) of a flow length (L) to a flowthickness (T) in the injection molding of the polyester (P-5) at 290° C.is measured in the following manner.

In the first place, 2 kg of a particularly polyester (P-5) (polyesterpellets) is dried for 16 hours or more under the conditions of atemperature of 140° C. and a pressure of 10 Torr using a tray dryer, toallow the particulate polyester (P-5) to have a water content of notmore than 50 ppm.

Then, the thus dried sample is molded by an injection molding machine ofM70B model manufactured by Meiki Seisakusho K.K. at a cylindertemperature of 290° C. using a L/T mold manufactured by MitsuiChemicals, Inc. and setting the mold temperature at 15° C. the moldingconditions are as follows.

-   -   Injection pressure: 120 kg/cm² (gauge pressure)    -   Injection rate: 90%    -   Metering position: 40 mm (constant)    -   Injection time: 10 seconds (constant)    -   Cooling time: 20 seconds (constant)

The L/T mold has a cavity in a shape of 125 cm (length)×10 mm (width)×2mm (thickness) and is provided with a gate at the lengthwise end.

The injected resin flows spirally and radially from the gate portion inthe cavity to melt and the molten resin moves in the cavity with keepingits shape of 10 mm in width and 2 mm in thickness (T).

Samples for the L/T measurement are those of the eleventh shot to thetwentieth shot from the beginning of molding. The flow lengths (L) ofthe samples are measured, an average of the lengths is calculated, andL/T is then calculated.

The intrinsic viscosity (X) of the molded product obtained by theinjection molding is determined as follows. A solution of a sample in amixed solvent of phenol/1,1,2,2-tetrachloroethane (50/50 by weight)having a concentration of 0.5 g/dl is prepared, then the solutionviscosity of the sample solution is measured at 25° C., and from thesolution viscosity, the intrinsic viscosity is calculated. The samplefor the intrinsic viscosity measurement is selected from the samples forthe L/T measurement.

The polyester (P-5) has the above relation between the ratio (Y) of aflow length to a flow thickness in the injection molding of thepolyester at 290° C. and the intrinsic viscosity (X) of a molded productobtained by the injection molding, and the polyester (P-5) having suchrelation exhibits high melt flowability and excellent moldability.

In the polyester (P-5), the titanium atom content is in the range ofpreferably 1 to 100 ppm, particularly preferably 1 to 80 ppm, and themagnesium atom content is in the range of preferably 1 to 200 ppm,particularly preferably 1 to 100 ppm. The weight ratio (Mg/Ti) of themagnesium atom to the titanium atom contained in the polyester (P-5) isdesired to be not less than 0.01, preferably 0.06 to 10, particularlypreferably 0.06 to 5. The polyester (P-5) having a weight ratio (Mg/Ti)of the magnesium atom to the titanium atom in the above range tends tohave excellent transparency. The chlorine content in the polyester (P-5)is preferably in the range of 0 to 1000 ppm, particularly preferably 0to 100 ppm.

The polyester (P-5) having the above properties can be produced by, forexample, the following process.

An aromatic dicarboxylic acid or an eater-forming derivative thereof andan aliphatic diol or an ester-forming derivative thereof, preferably,terephthalic acid or an ester-forming derivative thereof and ethyleneglycol or ester-forming derivative thereof, and if necessary, theaforesaid dicarboxylic acids, diols and polyfunctional compounds areused as starting materials, and they are subjected to the esterificationstep, the liquid phase polycondensation step, and if necessary, thesolid phase polycondensation step using the below-describedpolycondensation catalyst, whereby the polyester (D-5) can be obtained.

As the polycondensation catalyst, a titanium compound catalyst isemployable, and examples thereof include titanium alkoxides, such astitanium butoxide and titanium tetrasiopropoxide; organic titaniumcompound, such as acetylacetonato salt of titanium; and hydrolyzatesobtained by hydrolysis of titanium alkoxides or hydrolysis of titaniumhalides. Hydrolysis of the titanium akaloides or the titanium halidesmay be carried out in the presence of the compound of another element.

In the production of the polyester (P-5), it is preferable to use theaforesaid hydrolyzate (I-m) or (I-n) (titanium-containing hydrolyzate(A-2)) as the polycondensation catalyst.

The titanium-containing hydrolyzate (A-2) is used in combination with aco-catalyst component (II), if necessary.

Examples of the co-catalyst components (II) include the sameco-catalysts compounds as provisory described. Of these, preferable aremagnesium compounds such as magnesium carbonate and magnesium acetate;calcium compounds such as calcium carbonate and calcium acetate; andzinc compounds such as zinc chloride and zinc acetate. The co-catalystcompounds can be used singly or in combination of two or more kinds.

When the magnesium compound is used as the co-catalyst component (II),polyethylene terephthalate having excellent transparency is obtained.

The co-catalyst compound (II) is desirably used in such an amount thatthe molar ratio ((II)/(II)) of the metal atom (II) in the co-catalystcomponent to titanium (and another element if the titanium-containinghydrolyzate (A-2) contains another element) (I) in the polycondensationcatalyst is in the range of 1/50 to 50/1, preferably 1/40 to 40/1, morepreferably 1/30 to 30/1. When a phosphorus compound such as a phosphateor a phosphite is used, the amount thereof is an amount in terms of ametal atom contained in the phosphorus compound.

The polycondensation catalyst is used in an amount of usually 0.0005 to0.2% by weight, preferably 0.001 to 0.05% by weight, in terms of weightof a metal in the polycondensation catalyst, based on the weight of themixture of the aromatic dicarboxylic acid and the aliphatic diol. Whenthe aforesaid stabilizer is used, the amount thereof is in the range ofusually 0.001 to 0.1% by weight, preferably 0.002 to 0.02% by weight, interms of a phosphorus atom in the stabilizer. The polycondensationcatalyst and the stabilizer can be fed in the esterification reactionstep, or can be fed to the reactor of the first stage of thepolycondensation reaction step.

The intrinsic viscosity of the polyester (P-5) obtained as above isdesired to be usually not less than 0.50 dl/g, preferably 0.50 to 1.50dl/g, more preferably 0.72 to 1.0 dl/g. The density of the polyester(P-5) is desired to be usually not less than 1.37 g/cm³, preferably 1.37to 1.44 g/cm³, more preferably 1.38 to 1.43 g/cm³, still more preferably1.39 to 1.42 g/cm³.

When the ratio (L/T) of a flow length (L) to a flow thickness (T) in theinjection molding of the polyester (P-5) at 290° C. is taken as Y andthe intrinsic viscosity of a molded product obtained by the injectionmolding is taken as X (dl/g), X and Y satisfy the relation Y ≧2647−500X. Further, the polyester (P-5) desirably has a titanium atomcontent of 1 to 100 ppm, particularly 1 to 80 ppm, and a magnesium atomcontent of 1 to 200 ppm, particularly 1 to 100 ppm. The weight ratio(Mg/Ti) of the magnesium atom to the titanium atom contained in thepolyester (P-5) is desired to be not less than 0.01, preferably 0.06 to10, particularly preferably 0.06 to 5. When the polycondensationcatalysts (I) is used as a polycondensation catalyst and the co-catalystcomponent (II) is optionally used in combination, the resultingpolyester (P-5) exhibits excellent tint and transparency and has a lowacetaldehyde content and a low content of an oligomer such as a cyclictrimer.

The polyester (P-5) produced as above may contain additives hithertoknown, such as stabilizer, release agent, antistatic agent, dispersentand colorant (e.g., dye, pigment). These additives may be added in anystep of the process for producing the polyester (P-5), and may be addedby forming a masterbatch before molding.

The polyester (P-5) can be used as a material of various moldedproducts. For example, the polyester (P-5) is melt molded and used asblow molded articles (e.g., bottles), sheets, films, fibers, etc., butit is particularly preferably used as bottles.

In order to produce bottles, sheets, films, fibers, etc. from thepolyester (P-5), hitherto known processes are available.

The polyester (P-5) has high melt flowability and exhibits excellentmoldability when molded into blow molded articles, films, sheets, fibersand the like.

The preform for a blow molded article and the blow molded articleaccording to the invention are obtained from the polyester (P-5) andhave excellent transparency.

EFFECT OF THE INVENTION

The catalyst for polyester production according to the invention canproduce a polyester with higher catalytic activity as compared with agermanium compound or an antimony compound which has been heretoforeused as a polycondensation catalyst. According to the invention, apolyester having more excellent transparency and tint and loweracetaldehyde content can be obtained as compared with the case of usingan antimony compound as a polycondensation catalyst.

The catalyst for polyester production according to the invention, whichcomprises the solid titanium compound (I-a) and/or thetitanium-containing solid compound (I-b), and if necessary, theco-catalyst component (II), can produce a polyester with highercatalytic activity as compared with a germanium compound or an antimonycompound which has been heretofore used as a polycondensation catalyst.Further, when this catalyst is used, a polyester having more excellenttransparency and tint and lower acetaldehyde content can be obtained ascompared with the case of using an antimony compound as apolycondensation catalyst. Furthermore, a polyester, e.g., polyethyleneterephthalate, obtained by the use of the catalyst of the invention anda molded product formed therefrom have excellent transparency and tintand have a low acetaldehyde content.

The catalyst for polyester production according to the invention, whichcomprises the solid titanium compound (I-c) and the co-catalystcomponent (II) or comprises the titanium-containing solid compound (I-d)and if necessary the co-catalyst component (II), can produce a polyesterwith higher catalytic activity as compared with a germanium compound oran antimony compound which has been heretofore used as apolycondensation catalyst. Further, when this catalyst is used, apolyester having more excellent transparency and tint and loweracetaldehyde content can be obtained as compared with the case of usingan antimony compound as a polycondensation catalyst.

The catalyst for polyester production according to the invention, whichcomprises the solid titanium compound (I-e), the solid titanium compound(I-f), the titanium-containing solid compound (I-g) or thetitanium-containing solid compound (I-h), and if necessary, theco-catalyst component (II), can produce a polyester with higher catalystactivity as compared with a germanium compound or an antimony compoundwhich has been heretofore used as a polycondensation catalyst. Further,when this catalyst is used, a polyester having more excellenttransparency and tint and lower acetaldehyde constant can be obtained ascompared with the case of using an antimony compound as apolycondensation catalyst.

The catalyst for polyester production according to the invention, whichcomprises the solid titanium compound (I-i) and if necessary theco-catalyst component (II), can produce a polyester with highercatalytic activity as compared with a germanium compound or an antimonycompound which has been heretofore used as a polycondensation catalyst.Further, when this catalyst is used, a polyester having more excellenttransparency and tint and lower acetaldehyde content can be obtained ascompared with the case of using an antimony compound as apolycondensation catalyst.

The catalyst for polyester production according to the invention, whichcomprises a slurry obtained by heating a mixture of (A-1) thehydrolyzate (I-j) or the hydrolyzate (I-k), (B) the basic compound and(C) the aliphatic diol, can produce a polyester having a desiredintrinsic viscosity for a short period of time.

The catalyst for polyester production according to the invention, whichcomprises (A-2) the hydrolyzate (I-m) or the hydrolyzate (I-n) and (D)the metallic phosphate, or the catalyst for polyester productionaccording to the invention, which comprises a slurry obtained by heatinga mixture of (A-2) the hydrolyzate (I-m) or the hydrolyzate (I-n), (E)the metallic compound, (F) the phosphorus compound and (G) the aliphaticdiol, can produce a polyester having a low acetaldehyde content withhigh polymerization activity.

By the process for producing a polyester according to the inventionwherein a catalyst comprising the catalyst component (I) which comprisesthe hydrolyzate (I-j) or the hydrolyzate (I-k) and the co-catalystcomponent (II) is used as a polycondensation catalyst and the catalystcomponent (I) is added to the esterification reactor before thebeginning of the esterification reaction or immediately after thebeginning of the esterification reaction, a polyester having a desiredintrinsic viscosity can be obtained for a short period of time.

By the process for producing a polyester according to the inventionwherein an aromatic dicarboxylic acid or an ester-forming derivativethereof and an aliphatic diol or an ester-forming derivative thereof arepolycondensed in the presence of a polycondensation catalyst selectedfrom (1) a polycondensation catalyst comprising the hydrolyzate (I-m),(2) a polycondensation catalyst comprising the hydrolyzate (I-n) and (3)a polycondensation catalyst comprising the hydrolyzate (I-m) or thehydrolyzate (I-n) and a metallic compound, a phosphate or a phosphite,and in the presence of at least one compound selected from cycliclactone compounds and hindered phenol compounds, a polyester can beproduced with high polymerization activity, and the resulting polyesterhas a low acetaldehyde content.

By the process for producing a polyester according to the inventionwherein a catalyst comprising the polycondensation catalyst component(I) which comprises the hydrolyzate (I-m) or the hydrolyzate (I-n) andthe co-catalyst component (II) is used and a tint adjusting agent isadded in the esterification step or the polycondensation step, apolyester having an excellent tint can be produced with highpolymerization activity.

By the method for treating a polyester according to the invention, apolyester having small increase of the acetaldehyde content and smalldecrease of the intrinsic viscosity in the molding process can beobtained.

The polyester (P-1) according to the invention has excellenttransparency and tint and has a low acetaldehyde content.

The polyester (P-2) according to the invention has excellent tint.

The polyester (P-3) according to the invention a low acetaldehydecontent and is remarkably inhibited in increase of the acetaldehydecontent when molded into a molded product. For example, when a bottle orthe like is produced from the polyester (P-3), flavor or scent of thecontents filled in the bottle is hardly deteriorated.

The polyester (P-4) according to the invention has a low cyclic trimercontent, and the amount of the cyclic trimer produced in the molding ofthe polyester is small.

The polyester (P-5) according to the invention has high melt flowabilityand exhibits excellent moldability when molded into a blow moldedarticle, a film, a sheet, a fiber or the like.

EXAMPLE

The present invention is further described with reference to thefollowing examples, but it should be construed that the invention is inno way limited to those examples.

Example 495-1 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasseparated from the supernatant liquid by centrifugation of 2500revolutions for 15 minutes. Then, the resulting titanium hydroxideprecipitate was washed five times with deionized water. After thewashing, solid-liquid separation was carried out by centrifugation of2500 revolutions for 15 minutes. The washed titanium hydroxide wasvacuum dried at 70° C. under a pressure of 10 Torr for 18 hours toremove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 10μ.

The absorbed water content in the solid titanium compound thus obtainedwas measured by a Karl Fischer's water content meter. As a result, theabsorbed water content was 6.73% by weight. Further, the weight loss onheating was measured by thermogravimetry. As a result, the weight of thecompound was reduced by 7.50% by weight on heating up to 280° C. and wasfurther reduced by 2.17% by weight on heating from 280° C. to 600° C.,based on the initial weight, and this weight loss proved to be due todesoprtion of water content and a nitrogen compound. In the catalyst,nitrogen was contained in an amount of 1.3% by weight and chlorine wascontained in an amount of only 14 ppm. Therefore, it is presumed thatnitrogen is derived from not ammonium chloride but ammonia. The titaniumcontent in the solid titanium compound, as measured by a high-frequencyplasma emission analyzer, was 46% by weight.

From the above, the molar ratio between titanium and hydroxyl group inthe solid titanium compound was found to be 1:0.157. Nitrogen andchlorine was analyzed by an all nitrogen microanalyzer(chemiluminescence method) and a chromatography, respectively, and forthe calculation of the contents, they were considered to be desorbed asammonia and hydrogen chloride, respectively.

Example 495-2 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. To the deionized water, 0.15 g of anhydrous magnesiumhydroxide was added to give a dispersion. The dispersion in the beakerwas cooled in an ice bath, and thereto was dropwise added 5 g oftitanium tetrachloride with stirring. The liquid became acidic, and themagnesium hydroxide was dissolved. When production of hydrogen chloridestopped, the beaker containing the reaction solution was taken out ofthe ice bath, and 25% aqueous ammonia was dropwise added with stirring,to adjust pH of the solution to 8. The precipitate oftitanium-containing complex hydroxide produced was separated from thesupernatant liquid by centrifugation of 2500 revolutions for 15 minutes.Then, the precipitate of titanium-containing complex hydroxide waswashed five times with deionized water. After the washing, solid-liquidseparation was carried out by centrifugation of 2500 revolutions for 15minutes. The washed titanium-containing complex hydroxide was vacuumdried at 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

In the titanium-containing solid compound, the ratio between titaniumatom and magnesium atom was 91:9 by mol. By thermogravimetry, the molarratio between titanium and hydroxyl group in the titanium-containingsolid compound proved to be 1:0.31. Prior to use as a polycondensationcatalyst, the titanium-containing solid compound was pulverized inparticles of about 10μ.

Example 495-3 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. To the deionized water, 0.16 g of colloidal silica (tradename: Snowtex OXS) was added to give a dispersion. The dispersion in thebeaker was cooled in an ice bath, and thereto was dropwise added 5 g oftitanium tetrachloride with stirring. The liquid became acidic, and thecolloidal silica was dissolved. When production of hydrogen chloridestopped, the beaker containing the reaction solution was taken out ofthe ice bath, and 25% aqueous ammonia was dropwise added with stirring,to adjust pH of the solution to 8. The precipitate oftitanium-containing complex hydroxide produced was separated from thesupernatant liquid by centrifugation of 2500 revolutions for 15 minutes.Then, the precipitate of titanium-containing complex hydroxide waswashed five times with deionized water. After the washing, solid-liquidseparation was carried out by centrifugation of 2500 revolutions for 15minutes. The washed titanium-containing complex hydroxide was vacuumdried at 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

In the titanium-containing solid compound, the ratio between titaniumatom and silicon atom was 94:6 by mol. By thermogravimetry, the molarratio between titanium and hydroxyl group in the titanium-containingsolid compound proved to be 1:0.60. Prior to use as a polycondensationcatalyst, the titanium-containing solid compound was pulverized intoparticles of about 10μ.

Example 495-4 Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6458 parts by weight/hr) and ethyleneglycol (2615 parts by weight/hr) was continuously fed with stirringunder the conditions of a temperature of 260° C. and a pressure of 0.9kg/cm²-G in a nitrogen atmosphere, to perform esterification reaction.In the esterification reaction, a mixture of water and ethylene glycolwas distilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that the average residence time wascontrolled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Using the solid titanium compound prepared in Example 495-1 as apolycondensation catalyst, liquid phase polycondensation reaction of thelow condensate was conducted.

The amount of the solid titanium compound added as the catalyst was0.005% by mol in terms of titanium atom, based on the terephthalic acidunit in the low condensate. The polycondensation reaction was carriedout under the conditions of a temperature of 285° C. and a pressure of 1Torr.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was95 minutes.

Example 495-5

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that the titanium-containing solid compoundprepared in Example 495-2 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was76 minutes.

Example 495-6

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that the titanium-containing solid compoundprepared in Example 495-3 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was85 minutes.

Example 495-7

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that magnesium carbonate was used as thepolycondensation catalyst in addition to the solid titanium compoundprepared in Example 495-1. The amount of magnesium carbonate added was0.005% by mol in terms of magnesium atom, based on the terephthalic acidunit in the low condensate.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was75 minutes.

Example 495-8

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that magnesium acetate was used as thepolycondensation catalyst in addition to the solid titanium compoundprepared in Example 495-1. The amount of magnesium acetate added was0.005% by mol in terms of magnesium atom, based on the terephthalic acidunit in the low condensate.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was70 minutes.

Example 495-9

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that the solid titanium compound prepared inExample 495-1 was stored in a closed container at room temperature for 2months prior to use as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was101 minutes.

It can be seen from this example that the solid titanium compoundaccording to the invention is free from deterioration with time and hadgood storage properties. For reference, it is shown in a comparativeexample of Japanese Patent Publication No. 26597/1972 that orthotitanicacid is deteriorated with time and lowered in the polycondensationactivity.

Comparative Example 495-1

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that antimony acetate that was industrially usedwas used as the polycondensation catalyst. The amount of antimonyacetate added was 0.025% by mol in terms of antimony, abased on theterephthalic acid unit in the low condensate.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was120 minutes.

Comparative Example 495-2 Preparation of Titanium Compound

The titanium hydroxide obtained after washing with deionized water inExample 495-1 was boiled at 100° C. for 2 hours and then dried, toobtain a titanium compound.

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 495-4, except that the titanium compound obtained above was usedas the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was185 minutes.

It is known that titanium hydroxide is converted into metatitanic acedwhen heated in water, and the titanium compound obtained by way ofmetatitanic acid has beer found to have low polycondensation activity.

Example 496-7

To an esteriafion reactor, 76.81 mol of high-purity terephthalic acidand 86.03 mol of ethylene glycol were fed at 100° C. at atmosphericpressure. Then, 0.0045 mol of the titanium-containing solid compoundprepared in Example 495-2 was further added as a catalyst. Thereafter,the temperature of the reactor was raised to 260° C., and the reactionwas conducted for 340 minutes under a pressure of 1.7 kg/cm²-G in anitrogen atmosphere. Water produced by the reaction was continuallydistilled off from the system.

The total amount of the reaction solution in the esterification reactorwas transferred into a polycondensation reactor beforehand set at 260°C. Then, a solution of 0.0073 mol of tributyl phosphate in 6.44 mol ofethylene glycol was further added to the reactor at atmosphericpressure, and the temperature of the reactor was raised to 280° C. from260° C., while the pressure was reduced down to 2 Torr from atmosphericpressure.

The reaction in the polycondensation reactor was further conducted for108 minutes. Then, the reaction product was drawn out of thepolycondensation reactor in the form of strands. The strands wereimmersed in water, cooled and cut into particles by a strand cutter toobtain polyethylene terephthalate. The intrinsic viscosity of thepolyethylene terephthalate was 0.65 dl/g, the titanium content and themagnesium content as measured by atomic absorption analysis were 25 ppmand 2 ppm, respectively, and the Mg/Ti weight ratio was 0.08.

The polyethylene terephthalate obtained by the liquid phasepolymerization was then transferred into a solid phase polymerizationtower, crystallized at 170° C. for 2 hours in a nitrogen atmosphere, andthen subjected to solid phase polymerization at 210° C. for 13 hours toobtain particulate polyethylene terephthalate. The intrinsic viscosityof the polyethylene terephthalate was 0.825 dl/g. Using the polyethyleneterephthalate, a stepped square plate molded product was produced in thesame method as described above. The haze of part C of the stepped squareplate molded product was 17.8%.

Examples 496-8 to 495-13 Example 491-2C

Polyethylene terephthalate was produced in the same manner as in Example496-7, except that the catalyst and the polymerization conditions werechanged as shown in Table 496-1. The results are set forth in Table496-1.

Comparative Example 496-1 Preparation of Titanium Compound

The titanium hydroxide obtained after washing with deionized water inExample 495-1 was boiled at 100° C. for 2 hours and then dried, toobtained a titanium compound.

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 496-7, except that the titanium compound obtained above was usedas the polycondensation catalyst.

The time (liquid chase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was263 minutes.

It is known that titanium hydroxide is converted into metatitanic acidwhen heated in water, and the titanium compound obtained by way ofmetatitanic acid has been found to have low polycondensation activity.

The titanium content and the magnesium content in the polyethyleneterephthalate were 25 ppm and 16 ppm, respectively, the Mg/Ti ratio (byweight) was 0.64, and the chlorine content in the polyethyleneterephthalate was not more than 1 ppm.

TABLE 496-1 Liquid phase Solid phase Polycondensation catalyst (I)Co-catalyst component (II) polymerization polymerization Amount added *3Residue *4 Amount added *3 Residue *4 Time IV Time IV Haze Type (% bymol) (ppm) Type (% by mol) (ppm) (hr) (dl/g) (hr) (dl/g) (%) Ex.496-8 *10.013 31 — — — 2.62 0.643 23.0 0.816 16.5 Ex.496-9 *2 0.013 27 Mg(OAc)₂0.020 22 0.93 0.657 10.0 0.803 1.5 Ex.496-10 *2 0.013 13 Mg(OAc)₂ 0.02025 1.03 0.660 17.0 0.843 0.4 Ex.496-11 *2 0.013 25 Mg(OAc)₂ 0.020 161.70 0.651 12.5 0.820 13.7 Ex.496-12 *2 0.013 30 Ca(OAc)₂ 0.020 36 2.530.644 21.0 0.814 22.4 Ex.496-13 *2 0.013 29 Zn(OAc)₂ 0.020 59 1.12 0.66510.5 0.807 13.7 Ex.496-2C *2 0.013 29 — — — 3.63 0.653 26.0 0.834 19.4*1: titanium-containing solid compound prepared in Example 495-3 *2:solid titanium compound prepared in Example 495-1 *3: in terms of metalatom based on terephthalic acid unit *4: contents of metal atom based onparticulate polyethylene terephthalate Mg(OAc)₂: magnesium acetateCa(OAc)₂: calcium acetate Zn(OAc)₂: zinc acetate

Example 473-1 Preparation of solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added at room temperature with stirring, toadjust pH of the solution to 9. To the solution, a 15% acetic acidaqueous solution was dropwise added at room temperature with stirring,to adjust pH of the solution to 5. The resulting precipitate wasseparated by flirtation and washed 5 times with deionized water. Afterthe washing, solid-liquid separation was carried out by filtrationsimilarly to the above. The washed titanium compound was vacuum dried at70° C. udner a pressure of 10 Torr for 18 hours to remove water content,whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 10μ.

The absorbed water content in the solid titanium compound thus obtainedwas measured by a Karl Fischer's water content meter. As a result, theabsorbed water content was 11.29% by weight. Further, the weight loss onheating was measured by thermogravimetry. As a result, the weight losson heating up to 600° C. was 13.65% by weight. Measurements of titaniumcontent, nitrogen content and chlorine content in the solid titaniumcompound resulted in 43% by weight, 510 ppm and 76 ppm, respectively.From these results, the molar ratio between titanium and hydroxyl groupin the solid titanium compound was found to be 1:0.28. The titaniumcontent was measured by atomic absorption analysis. Nitrogen andchlorine were analyzed by an all nitrogen microanlayzer(chemiluminescence method) and chromatography, respectively, and for thecalculation of the contents, they were considered to be desorbed asammonia and hydrogen chloride, respectively.

Example 473-2 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added at room temperature with stirring, toadjust pH of the solution to 5. The resulting precipitate was separatedby filtration and washed 5 times with deionized water. After thewashing, solid-liquid separation was carried out by filtration similarlyto the above. The washed titanium compound was vacuum dried at 70° C.under a pressure of 10 Torr for 18 hours to remove water content,whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 10μ.

With respect to the solid titanium compound obtained above, absorbedwater content, weight loss on heating up to 600° C., titanium content,nitrogen content and chlorine content were measured in the same manneras in Example 473-1. As a result, the water content measured by a KarlFischer's water content meter was 14.35% by weight, the weight loss onheating up to 600° C. was 16.82% by weight, the titanium content was 40%by weight, the nitrogen content was 950 ppm, and the chlorine contentwas 54 ppm. From these results, the molar ratio between titanium andhydroxyl group in the solid titanium compound was found to be 1:0.31.

Example 473-3 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added at room temperature with stirring, toadjust pH o0 to solution to 3.5. The resulting precipitate was separatedby filtration and washed 5 times with deionized water. After thewashing, solid-liquid separation was carried out by filtration similarlyto the above. The washed titanium compound was vacuum dried at 70° C.under a pressure of 10 Torr for 18 hours to remove water content,whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyze, the solid titanium compoundwas pulverized into particles of about 10μ.

With respect to the solid titanium compound obtained above, absorbedwater content, weight loss on heating up to 600° C., titanium content,nitrogen content and chlorine content were measured in the same manneras in Example 473-1. As a result, the water content measured by a KarlFischer's water content meter was 12.24% by weight, the weight loss onheating up to 600° C. was 14.36% by weight, the titanium content was 41%by weight, the nitrogen content was 150 ppm, and the chloride contentwas 26 ppm. From these results, the molar ratio between titanium andhydroxyl gruop in the solid titanium compound was found to be 1:0.27.

Example 473-4 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and a 5%sodium hydroxide aqueous solution was dropwise added at room temperaturewith stirring, to adjust pH of the solution to 5. The resultingprecipitate was separated by filtration and washed 5 times withdeionized water. After the washing, solid-liquid separation was carriedout by filtration similarly to the above. The washed titanium compoundwas vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours toremove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 10μ.

With respect to the solid titanium compound obtained above, absorbedwater content, weight loss on heating up to 600° C., metallic titaniumcontent, metallic sodium content and chlorine content were measured inthe same manner as in Example 473-1. As a result, the water contentmeasured by a Karl Fischer's water content meter was 12.37% by weight,the weight loss on heating up to 600° C. was 10.12% by weight, thetitanium content was 40% by weight, and the chlorine content was 54 ppm.Sodium was not detected. From these results, the molar ratio betweentitanium and hydroxyl group in the solid titanium compound was found tobe 1:0.30.

Example 473-5 Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6458 parts by weight/hr) and ethyleneglycol (2615 part by weight/hr) was continuously fed with stirring underthe conditions of a temperature of 260° C. and a pressure of 0.9kg/cm²-G in a nitrogen atmosphere, to perform esterification reaction.In the esterification reaction, a mixture of water and ethylene glycolwas distilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that the average residence time wascontrolled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Using the solid titanium compound prepared in Example 473-1 andmagnesium acetate as polycondensation catalysts, liquid phasepolycondensation reaction of the low condensate was conducted.

The amount of the solid titanium compound added as the catalyst was0.01% by mol in terms of titanium atom and the around of magnesiumacetate added as the catalyst was 0.02% by mol in terms of magnesiumatom, each amount being based on the terephthalic acid unit in the lowcondensate.

The polycondensation reaction was conducted under the conditions of atemperature of 280° C. and a pressure of 1 Torr. As a result, the time(liquid phase polycondensation time) required to attain an intrinsicviscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 58minutes.

Example 473-6

Polycondensation reaction was carried out in the same manner as inExample 473-5, except that the solid titanium compound prepared inExample 473-2 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was60 minutes.

Example 473-7

Polycondensation reaction was carried out in the same manner as inExample 473-5, except that the solid titanium compound prepared inExample 473-3 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was67 minutes.

Example 473-8

Polycondensation reaction was carried out in the same manner as inExample 473-5, except that the solid titanium compound prepared inExample 473-4 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was65 minutes.

Comparative Example 473-1

Polycondensation reaction was carried out in the same manner as inExample 473-5, except that antimony acetate that was industrially usedwas used as the polycondensation catalyst. The amount of antimonyacetate added was 0.025% by mol in terms of antimony, based on theterephthalic acid unit in the low condensate.

The time (liquid phase polycondensation time) required to attain anintrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was120 minutes.

Example 510-1 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. At this time, the temperature or the solution was 0 to 5° C.When production of hydrogen chloride stopped, the beaker containing thereaction solution was taken out of the ice bath, and 25% aqueous ammoniawas dropwise added with stirring, to adjust pH of the solution to 8. Atthis time, the temperature of the solution was 0 to 10° C. Theprecipitate of titanium hydroxide produced was filtered under a pressureof 4 kg/cm²-G through a pressure filter and separated. Thereafter, theprecipitate of titanium hydroxide was washed 5 times with deionizedwater. After the washing, solid-liquid separation was carried out bypressure filtration under a pressure of 4 kg/cm²-G similarly to theabove. The washed titanium hydroxide was vacuum dried at 70° C. under apressure of 10 Torr for 18 hours to remove water content, whereby asolid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 50μ.

As a result of analysis of the sol-d titanium compound, the titaniumcontent was 40% by weight, the nitrogen content was 950 ppm, thechlorine content was 54 ppm, the weigh: loss on heating up to 600° C.was 16.8% by weight, and the absorbed water content was 15.25% byweight. The OH/Ti ratio calculated from these results was 0.193.Measurement of crystallinity resulted in 0%, and this solid titaniumcompound was completely amorphous.

In Examples 510-1 and 510-2 and Comparative Examples 510-1 and 510-2,X-ray diffraction intensity was measured under the following conditions.

-   -   X-ray: Cu K-ALPHA1/50 kV/300 mA    -   Goniometer: RINT2000 wide angle goniometer    -   Attachment: standard sample holder    -   Filter: none    -   Counter monochrometer: fully automatic monochrometer    -   Divergence slit: ½ deg.    -   Scattering slit: ½ deg.    -   Light receiving slit: 0.15 mm    -   Counter: scintillation counter    -   Scanning mode: continuous    -   Scanning speed: 4°/min    -   Scanning step: 0.02°    -   Scanning axis: 2θ/θ    -   Scanning range: 1.5-70°    -   θ Offset: 0°    -   Fixed angle: 0°

Production of Polyester

To a reactor in which 33500 parts of weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6458 parts by weight/hr) and ethyleneglycol (2615 parts by weight/hr) was continuously fed with stirringunder the conditions of a temperature of 260° C. and a pressure of 0.9kg/cm²-G in a nitrogen atmosphere, to perform esterification reaction.In the esterification reaction, a mixture of water and ethylene glycolwas distilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that the average residence time wascontrolled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Using the solid titanium compound prepared above and magnesium acetateas polycondensation catalysts, polycondensation reaction of the lowcondensate was conducted.

The amount of the solid titanium compound added as the catalyst was0.0105% by mol in terms of titanium atom, based on the terephthalic-cacid unit in the low condensate, and the amount of magnesium acetateadded as the catalyst was 0.021% by mol in terms of magnesium atom,based on the terephthalic acid unit in the low condensate. In thepolycondensation, tributyl phosphate was further added in an amount of0.0105% by mol in terms of phosphorus atom. The polycondensationreaction was conducted under the conditions of a temperature of 285° C.and a pressure of 1 Torr, to obtain polyethylene terephthalate (liquidphase polycondensation product) having an intrinsic viscosity of 0.65dl/g. The polycondensation time was 65 minutes.

Example 510-2 Preparation of Solid Titanium Compound

A solid titanium compound was obtained in the same manner as in Example510-1, except that the drying temperature is changed to 100° C. from 70°C.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 50μ.

As a result of analysis of the solid titanium compound, the titaniumcontent was 43% by weight, the nitrogen content was 510 ppm, thechlorine content was 71 ppm, the weight loss on heating up to 600° C.was 13.65% by weight, and the absorbed water contend was 12.11% byweight. The OH/Ti ratio calculated from these results was 0.182.Measurement of crystallinity resulted in 7%, and this solid titaniumcompound was slightly crystallized.

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 510-1, except that the solid titanium compound prepared abovewas used. As a result, polyethylene terephthalate (liquid phasepolycondensation product) having an intrinsic viscosity of 0.65 dl/g wasobtained. The polycondensation time was 68 minutes.

Comparative Example 510-1 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker, and thereto was dropwise added 5 g of titaniumtetrachloride with stirring. At this time, the temperature of thesolution was about 25° C. After production of hydrogen chloride stopped,the temperature of the solution was kept at 80° C., and 25% aqueousammonia was dropwise added with stirring, to adjust pH of the solutionto 8. The precipitate of titanium hydroxide produced was filtered undera pressure of 4 kg/cm²-G through a pressure filter and separated.Thereafter, the precipitate of titanium hydroxide was washed 5 timeswith deionized water. After the washing, solid-liquid separation wascarried out by pressure filtration under a pressure of 4 kg/cm²-Gsimilarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 50μ.

As a result of analysis of the solid titanium compound, the titaniumcontent was 50% by weight, the nitrogen content was 530 ppm, thechlorine content was 41 ppm, the weight loss on heating up to 600° C.was 16.63% by weight, and the absorbed water content was 14.68% byweight. The OH/Ti ratio calculated from these results was 0.200.Measurement of crystallinity resulted in 64%, and this solid titaniumcompound was considerably crystallized.

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 510-1, except that the solid titanium compound prepared abovewas used. However, an intrinsic viscosity of 0.65 dl/g could not beobtained by the polycondensation for a period up to 240 minutes.

Comparative Example 510-2 Preparation of Solid Titanium Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The temperature of the deionized water was kept at 60° C.,and 5 g of titanium tetrachloride was dropwise added with stirring.After production of hydrogen chloride stopped, the temperature of thesolution was kept at 80° C., and 25% aqueous ammonia was dropwise addedwith stirring, to adjust pH of the solution to 8. The precipitate oftitanium hydroxide produced was filtered under a pressure of 4 kg/cm²-Gthrough a pressure filter and separated. Thereafter, the precipitate oftitanium hydroxide was washed 5 times wish deionized water. After thewashing, solid-liquid separation was carried out by pressure filtrationunder a pressure of 4 kg/cm²-G similarly to the above. The washedtitanium hydroxide was vacuum dried at 100° C. under a pressure of 10Torr for 18 hours to remove water content, whereby a solid titaniumcompound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compoundwas pulverized into particles of about 50μ.

As a result of analysis of the solid titanium compound, the titaniumcontent was 47% by weight, the nitrogen content was 840 ppm, thechlorine content was 1050 ppm, the weight loss on heating up to 600° C.was 15.95% by weight, and the absorbed water content was 13.62% byweight. The OH/Ti ratio calculated from these results was 0.240.Measurement of crystallinity resulted in 71%, and this solid titaniumcompound was considerably crystallized.

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 510-1, except that the solid titanium compound prepared abovewas used. However, an intrinsic viscosity of 0.65 dl/g could not beobtained by the polycondensation for a period us to 240 minutes.

Example 198-1 498- 1 Preparation of Titanium-containing Hydrolyzate

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontend, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containingsolid compound was pulverized into particles of about 10 μm.

Preparation of Catalyst For Polyester Production

A mixture of 10 g of the titanium-containing hydrolyzate, 65 g ofethylene glycol and 25 g of tetraethylammonium hydroxide was heated at190° C. for 3 hours to obtain a catalyst for polyester production.

Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rate of 6458 parts by weight/hr and 2615 parts byeeight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)wad continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the catalyst for polyester production was addedin an amount of 0.021% by mol in terms of titanium atom, based on 1 molof the terephthalic acid unit in the low condensate, and liquid phasepolycondensation reaction was conducted under the conditions of atemperature of 285° C. and a pressure of 1 Torr. The time required toattain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalatewas 57 minutes.

Example 498-1C

Polycondensation reaction was carried out in he same manner as inExample 498-1, except that the titanium-containing hydrolyzate was usedin an amount of 0.021% by mol in terms of titanium atom, based on 1 molof the terephthalic acid unit in low condensate, instead of the catalystfor polyester production. The time required to attain an intrinsicviscosity of 0.65 dl/g of polyethylene terephthalate was 3 hours and 55minutes. The acetaldehyde content in the polyethylene terephthalate was52 ppm.

Comparative Example 498-2 Preparation of Polycondensation Catalyst (1)

A mixture of 10 g of the titanium-containing hydrolyzate, 65 g ofethylene glycol and 25 g of acetic acid was heated at 190° C. for 3hours to obtain a polycondensation catalyst (1).

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 498-1, except that the polycondensation catalyst (1) was used inan amount of 0.021% by mol in terms of titanium atom, based on 1 mol ofthe terephthalic acid unit in low condensate, instead of the catalystfor polyester production. The time required to attain an intrinsicviscosity of 0.65 dl/g of polyethylene terephthalate was 146 minutes.The acetaldehyde content in the polyethylene terephthalate was 58 ppm.

Comparative Example 498-3 Preparation of Polycondensation Catalyst (2)

A mixture of 10 g of the titanium-containing hydrolyzate and 90 g ofethylene glycol was heated at 190° C. for 3 hours to obtain apolycondensation catalyst (2).

Production of Polyester

Polycondensation reaction was carried out in the same manner as inExample 498-1, except that the polycondensation catalyst (2) was used inan amount of 0.021% by mol in terms of titanium atom, based on 1 mol ofthe terephthalic acid unit in low condensate, instead of the catalystfor polyester production. The time required to attain an intrinsicviscosity of 0.65 dl/g of polyethylene terephthalate was 1 hour and 50minutes.

Example 501-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containingsolid compound was pulverized into particles of about 10 μm.

Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at races of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

To the low condensate, the titanium-containing solid compound was addedin an amount of 0.021% by mol in terms of titanium atom, based on theterephthalic acid unit in the low condensate, magnesiumhydrogenphosphate was added in an amount of 0.021% by mol in terms ofmagnesium atom, based on the terephthalic acid unit in the lowcondensate, and phosphoric acid was added in an amount of 0.0105% by molin terms of phosphorus atom, and liquid phase polycondensation reactionwas conducted under the conditions of a temperature of 285° C. and apressure of 1 Torr. The time required to attain an intrinsic viscosityof 0.65 dl/g of polyethylene terephthalate was 57 minutes. Theacetaldehyde content in the resulting polyethylene terephthalate was 60ppm.

Example 501-2

Polycondensation reaction was carried out in the same manner as inExample 501-1, except that trimagnesium diphosphate was used instead ofmagnesium hydrogenphosphate. The time required to attain an intrinsicviscosity of 0.65 dl/g of polyethylene terephthalate was 67 minutes. Theacetaldehyde content in the resulting polyethylene terephthalate was 57ppm.

Example 501-1C

Polycondensation reaction was carried out in the same manner as inExample 501-1, except that magnesium acetate was used instead ofmagnesium hydrogenphosphate. The time required to attain an intrinsicviscosity of 0.65 dl/g of polyethylene terephthalate was 100 minutes.The acetaldehyde content in the resulting polyethylene terephthalate was70 ppm.

Example 497-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containingsolid compound was pulverized into particles of about 10 μm.

Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rates of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

Before the beginning of the esterification reaction, thetitanium-containing solid compound, magnesium acetate and tributylphosphate were added. The amount of the titanium-containing solidcompound added was 0.021% by mol in terms of titanium atom, based onterephthalic acid (unit), the amount of magnesium acetate added was0.021% by mol in terms of magnesium atom, based on the terephthalic acid(unit), and the amount of tributyl phosphate added was 0.0105% by mol interms of phosphate atom, based on the terephthalic aced (unit).

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

The low condensate thus obtained was subjected to liquid phasepolycondensation reaction under the conditions of a temperature of 285°C. and a pressure of 1 Torr. The time required to attain an intrinsicviscosity of 0.65 dl/g of polyethylene terephthalate was 56 minutes.

Example 497-1C

Polyethylene terephthalate was produced in the same manner as in Example497-1, except that the titanium-containing solid compound was not addedin the esterification reaction step but added to the reactor of thefirst step in the liquid phase polycondensation step. The time requiredto attain an intrinsic viscosity of 0.65 dl/g of polyethyleneterephthalate was 4 hours.

Example 499-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containingsolid compound was pulverized into particles of about 10 μm.

Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rates of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residenttime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

To the low condensate, the titanium-containing solid compound andtributyl phosphate were added, and liquid phase polycondensationreaction was conducted under the conditions of a temperature of 285° C.and a pressure of 1 Torr. The amount of the titanium-containing solidcompound added was 0.021% by mol in terms of titanium atom, based on 1mol of the terephthalic acid unit in the low condensate, and the amountof tributyl phosphate added was 0.0105% by mol in terms of phosphorusatom, based on 1 mol of the terephthalic acid unit. The time required toattain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalicwas 60 minutes.

Example 499-2

Polycondensation reaction was carried out in the same manner as inExample 499-1, except that trioctyl phosphate was used instead oftributyl phosphate. The time required to attain an intrinsic viscosityof 0.65 dl/g of polyethylene terephthalate was 60 minutes.

Example 499-3

Polycondensation reaction was carried out in the same manner as inExample 499-1, except that triphenyl phosphate was used instead oftributyl phosphate. The time required to attain an intrinsic viscosityof 0.65 dl/g of polyethylene terephthalate was 60 minutes.

Example 499-4

Polycondensation reaction was carried out in the same manner as inExample 499-1, except that trimethyl phosphate was used instead oftributyl phosphate. The time required to attain an intrinsic viscosityof 0.65 dl/g of polyethylene terephthalate was 75 minutes.

Example 500-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containingsolid compound was pulverized into particles of about 10 μm.

Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rates of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the titanium-containing solid compound, magnesiumacetate andtetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methanewere added, and liquid phase polycondensation reaction was conductedunder the conditions of a temperature of 285° C. and a pressure of 1Torr. The amount of the titanium-containing solid compound added was0.021% by mol in terms of titanium atom, based on the terephthalic acidunit in the low condensate, the amount of magnesium acetate added was0.021% by mol in terms of magnesium atom, based on the terephthalic acidunit in the low condensate, and the amount oftetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methaneadded was 600 ppm based on the low condensate.

The time required to attain an intrinsic viscosity of 0.65 dl/g ofpolyethylene terephthalate was 50 minutes. The acetaldehyde content inthe resulting polyethylene terephthalate was 60 ppm.

Example 500-2

Polycondensation reaction was carried out in the same manner as inExample 500-1, except thatbis(2,6-di-t-butyl-4-phenylmethyl)pentaerythritol diphosphite was usedin an amount of 300 ppm based on the low condensate instead oftetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g ofpolyethylene terephthalate was 48 minutes. The acetaldehyde content inthe resulting polyethylene terephthalate was 52 ppm.

Example 500-3

Polycondensation reaction was carried out in the same manner as inExample 500-1, except that 3,5-di-t-butyl-4-hydroxybenzylphosphoric aciddistearyl easter was used in an amount of 400 ppm based on the lowcondensate instead oftetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g ofPolyethylene terephthalate was 46 minutes. The acetaldehyde content inthe resulting polyethylene terephthalate was 58 ppm.

Example 500-4

Polycondensation reaction was carried out in the same manner as inExample 500-1, except that a mixture oftetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane,5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one andtris(2,4-di-t-butylphenly)phosphite (mixing ratio=42.5:15:42.5) was usedin an amount of 500 ppm based on the low condensate instead oftetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g ofpolyethylene terephthalate was 49 minutes. The acetaldehyde content inthe resulting polyethylene terephthalate was 55 ppm.

Example 500-5

Polycondensation reaction was carried out in the same manner as inexample 500-1, except that tributyl phosphate was used in an amount of0.0105% by mol in terms or phosphorus atom, based on the terephthalicacid in the low condensate, in addition totetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g ofpolyethylene terephthalate was 50 minutes. The acetaldehyde content inthe resulting polyethylene terephthalate was 50 ppm.

Example 500-1C

Polycondensation reaction was carried out in the same manner as inExample 500-1, except that phosphoric acid was used in an amount of0.0105% by mol in terms of phosphorus atom, based on the terephthalicacid unit in the low condensate, instead oftetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 gl/g ofpolyethylene terephthalate was 70 minutes. The acetaldehyde content inthe resulting polyethylene terephthalate was 70 ppm.

Example 502-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containingsolid compound was pulverized into particles of about 10 μm.

Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction wad conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rates of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

Before the beginning of the esterification reaction, thetitanium-containing solid compound, magnesium acetate, tributylphosphate and a tint adjusting agent were added to the reactor. Theamount of the titanium-containing solid compound added was 12 ppm interms of titanium atom, based on the polyethylene terephthalate, theamount of magnesium acetate added was 25 ppm in terms of magnesium atom,based on the polyethylene terephthalate, the amount of tributylphosphate added was 15 ppm in berms of phosphorus atom, based on thepolyethylene terephthalate, and the amount of the tint adjusting agent(Solvent Blue 104) added was 5.0 ppm based on the polyethyleneterephthalate.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

The low condensate thus obtained was subjected to liquid phasepolycondensation reaction under the conditions of a temperature of 285°C. and a pressure of 1 Torr.

The tint of the polyester chips obtained above was measured by a 45°diffusion type color difference meter (Nippon Denshoku SQ 300H Model).The result is set forth in Table 502-1.

Examples 502-2 to 502-5. Examples 502-1C

A polyester was produced in the same manner as in Example 502-1, exceptthat the type and the amount of the tint adjusting agent were changed asshown in Table 502-1. The tint of the polyester chips was measured. Theresult is set forth in Table 502-1.

Examples 502-6 to 502-11. Examples 502-2C to 502-4C

A polyester was produced in the same manner as in Example 502-1, exceptthat the amounts of the titanium-containing solid compound, magnesiumacetate and the phosphorus compound were changed as shown in Table 502-1and the type and the amount of the tint adjusting agent were changed asshown in Table 502-1. The tint of the polyester chips was measured. Theresult is set froth in Table 502-1.

TABLE 502-1 Titanium- containing solid Magnesium Phosphorus Tintadjusting agent (ppm) Tint compound acetate compound Solvent PigmentSolvent L a b (ppm) (ppm) (ppm) Blue 104 Red 263 Red 135 value valuevalue Ex. 502-1 12 25 15 5.0 — — 51.2 −7.4 −5.0 Ex. 502-2 ″ ″ ″ 5.0 3.0— 45.4 0.0 −7.0 Ex. 502-3 ″ ″ ″ 3.0 1.8 — 51.4 −0.7 −2.4 Ex. 502-4 ″ ″ ″1.0 0.6 — 58.8 −2.1 4.0 Ex. 502-5 ″ ″ ″ — 5.0 — 55.7 14.0 5.1 Ex. 502-1C″ ″ ″ — — — 65.9 −2.8 10.5 Ex. 502-6 18 18 30 2.0 1.5 — 71.5 −0.2 −1.1Ex. 502-7 ″ ″ ″ 2.5 — 2.5 53.4 −1.6 −0.4 Ex. 502-2C ″ ″ ″ — — — 65.4−2.5 8.8 Ex. 502-8 25 25 15 — — 5.0 56.7 10.2 10.7 Ex. 502-9 ″ ″ ″ — —2.0 61.0 3.6 10.1 Ex. 502-3C ″ ″ ″ — — — 64.8 −3.0 11.9 Ex. 502-10 18 1815 1.5 — 1.0 55.9 −2.8 1.5 Ex. 502-11 ″ ″ ″ 2.5 — 2.0 52.4 −2.0 −0.5 Ex.502-4C ″ ″ ″ — — — 65.8 −2.4 9.1

Example 46a-1

In a stainless steel container, 2.5 kg of particulate polyethyleneterephthalate having an intrinsic viscosity of 0.85 dl/g, a density of1.40 g/cm³ and an acetaldehyde content of 1.5 ppm was immersed in 4 kgof a trimethyl phosphate aqueous solution of 0.0695% by weight (161 ppmin terms of phosphorus atom), and they were kept at room temperature for4 hours. Thereafter, the particulate polyethylene terephthalate wasseparated from the trimethyl phosphate aqueous solution, hydro-extractedand then dried at 160° C. for 5 hours in a stream of nitrogen. Using theresulting polyethylene terephthalate, a stepped square plate moldedproduct was produced by the aforesaid method. The stepped square platemolded product has an acetaldehyde content of 7.7 ppm and an intrinsicviscosity of 0.821 dl/g.

Example 464-2

In a stainless steel container, 2.5 kg of the same particulatepolyethylene terephthalate as used in Example 464-1 was immersed in 4 kgof a trimethyl phosphate aqueous solution of 0.0595% by weight (161 ppmin terms of phosphorus atom). Then, the stainless steel containercontaining the polyethylene terephthalate and the trimethyl phosphateaqueous solution was externally heated to control the internaltemperature to 95° C. and kept for 4 hours to perform heat treatment.Thereafter, the particulate polyethylene terephthalate was separatedfrom the trimethyl phosphate aqueous solution, hydro-extracted and thendried at 160° C. for 5 hours in a stream of nitrogen. Using theresulting polyethylene terephthalate, a stepped square plate moldedproduct was produced by the aforesaid method. The stepped square platemolded product had an acetaldehyde content of 8.5 ppm and an intrinsicviscosity of 0.802 dl/g.

Example 46d-1C

The same particulate polyethylene terephthalate as used in Example 464-1was molded into a stepped square plate molded product by the aforesaidmethod, without performing a contact treatment with aphosphorus-containing aqueous solution. The stepped square plate moldedproduct had an acetaldehyde content of 11 ppm and an intrinsic viscosityof 0.833 dl/g.

Example a64-2C

Treatment of particulate polyethylene terephthalate was carried out inthe same manner as in Example 464-1, except that a phosphoric acidaqueous solution having the same concentration (0.0508% by weight, 161ppm in terms of phosphorus atom) was used instead of the trimethylphosphate aqueous solution. Using the resulting polyethyleneterephthalate, a stepped square plate molded product was produced by theaforesaid method. The stepped square plate molded product had anacetaldehyde content of 8.3 ppm and an intrinsic viscosity of 0.814dl/g.

Comparative Example 464-3

Treatment of particulate polyethylene terephthalate was carried out inthe same manner as in Example 464-2, except that a phosphoric acidaqueous solution was used instead of the trimethyl phosphate aqueoussolution. Using the resulting polyethylene terephthalate, a steppedsquare plate molded product was produced by the aforesaid method. Thestepped square plate molded product had an acetaldehyde content of 10.0ppm and an intrinsic viscosity of 0.788 dl/g.

Example 465-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use, the titanium-containing solid compound was pulverized intoparticles of about 10 μm.

Production of Polyethylene Terephthalate

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rates of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours. The number-average molecular weight ofthe low condensate of ethylene glycol and terephthalic acid was 600 to1300 (trimer to pentamer).

To the low condensate, the titanium-containing solid compound, magnesiumacetate and tributyl phosphate were added, and liquid phasepolycondensation reaction was conducted under the conditions of atemperature of 285° C. and a pressure of 1 Torr to obtain polyethyleneterephthalate having an intrinsic viscosity of 0.65 dl/g. The amount ofthe titanium-containing solid compound added was 0.021% by mol in termsof titanium atom, based on the terephthalic acid unit in the lowcondensate, the amount of magnesium acetate added was 0.021% by mol interms of magnesium atom, based on the terephthalic acid unit in the lowcondensate, and the amount of tributyl phosphate added was 0.0105% bymol in terms of phosphorus atom, based on the terephthalic acid unit inthe low condensate.

The polyethylene terephthalate in which the liquid phasepolycondensation had been completed was subjected to solid phasepolycondensation, to obtain particulate polyethylene terephthalatehaving an intrinsic viscosity of 0.81 dl/g, a density of 1.40 g/cm³ andan acetaldehyde content of 1.0 ppm.

Treatment of Polyethylene Terephthalate

Into a 100 ml flask, 10 g of the particulate polyethylene terephthalateand 40 g of isopropanol were introduced, and they were heated for 4hours under reflux. The mixture was dried at 70° C. for 16 hours, meltedby heating at 270° C. for 6 minutes and then cooled to room temperatureto give a sample. Measurement of acetaldehyde content in the sampleresulted in 5.2 ppm.

Example 465-2

Contact of particulate polyethylene terephthalate with an organicsolvent was carried out in the same manner as in Example 465-1, exceptthat methanol was used instead of isopropanol. Then, the acetaldehydecontent was measured in the same manner as in Example 465-1. As aresult, the acetaldehyde content was 6.4 ppm.

Example 465-3

Contact of particulate polyethylene terephthalate with an organicsolvent was carried out in the same manner as in Example 465-1, exceptthat acetone was used instead of isopropanol. Then, the acetaldehydecontent was measured in the same manner as in Example 465-1. As aresult, the acetaldehyde content was 6.7 ppm.

Example 465-4

Contact of particulate polyethylene terephthalate with an organicsolvent was carried out in the same manner as in Example 465-1, exceptthat hexane was used instead of isopropanol. Then, the acetaldehydecontent was measured in the same manner as in Example 465-1. As aresult, the acetaldehyde content was 6.8 ppm.

Example 465-1C

The same particulate polyethylene terephthalate as used in Example 465-1was dried at 70° C. for 16 hours, melted by heating at 270° C. for 6minutes and cooled to room temperature, without performing a contacttreatment with an organic solvent, to give a sample. Measurement ofacetaldehyde content in the sample resulted in 7.3 ppm.

Example 466-1 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. The deionized water in the beaker was cooled in an icebath, and thereto was dropwise added 5 g of titanium tetrachloride withstirring. When production of hydrogen chloride stopped, the beakercontaining the reaction solution was taken out of the ice bath, and 25%aqueous ammonia was dropwise added with stirring, to adjust pH of thesolution to 8. The precipitate of titanium hydroxide produced wasfiltered under a pressure of 3 kg/cm² through a pressure filter andseparated. Thereafter, the precipitate of titanium hydroxide was washed5 times with deionized water. After the washing, solid-liquid separationwas carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum driedat 70° C. under a pressure of 10 Torr for 18 hours to remove watercontent, whereby a titanium-containing solid compound was obtained.

Prior to use, the titanium-containing solid compound was pulverized intoparticles of about 10 μm.

Production of Polyethylene Terephthalate

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid and ethylene glycol was continuously fed,and esterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. The slurry of high-purity terephthalic acidand ethylene glycol was prepared by mixing high-purity terephthalic acidand ethylene glycol at rates of 6458 parts by weight/hr and 2615 partsby weight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycolwas distilled off. The esterification reaction product (low condensate)was continuously drawn out of the system so that the average residencetime was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the titanium-containing solid compound, magnesiumacetate and tributyl phosphate were added, and liquid phasepolycondensation reaction was conducted under the conditions of atemperature 285° C. and a pressure of 1 Torr to obtain polyethyleneterephthalate having an intrinsic viscosity of 0.65 dl/g. The amount ofthe titanium-containing solid compound added was 0.021% by mol in termsof titanium atom, based on the terephthalic acid unit in the lowcondensate, the amount of magnesium acetate added was 0.021% by mol interms of magnesium atom, based on the terephthalic acid unit in the lowcondensate, and the amount of tributyl phosphate added was 0.0105% bymol in terms of phosphorus atom, based on the terephthalic acid unit inthe low condensate.

The polyethylene terephthalate in which the liquid phasepolycondensation had been completed was subjected to solid phasepolycondensation, to obtain particulate polyethylene terephthalatehaving an intrinsic viscosity of 0.81 dl/g, a density of 1.40 g/cm³ andan acetaldehyde content of 1.0 ppm.

Treatment of Polyethylene Terephthalate

Into a 200 ml flask, 30 g of the particulate polyethylene terephthalate,60 g of isopropanol and 10.3 of tributyl phosphate (2% by weight interms of phosphorus atom based on isopropanol) were introduced, and theywere heated for 4 hours under reflux. Thereafter, he mixture was washedthree times with 60 g of isopropanol, dried at 70° C. for 16 hours,melted by heating at 285° C. for 10 minutes an then cooled to roomtemperature to give a sample. Measurement of an acetaldehyde content inthe sample resulted in 30 ppm.

Example 466-2

Contact of particulate polyethylene terephthalate with aphosphorus-containing organic solvent solution was carried out in thesame manner as in Example 466-1, except that methanol was used insteadof isopropanol and 5.4 g (2% by weight in terms of phosphorus atom basedon methanol) of trimethyl phosphate was used instead of 10.3 g oftributyl phosphate. Then, the acetaldehyde content was measured in thesame manner as in Example 466-1. As a result, the acetaldehyde contentwas 28 ppm.

Example 466-3

Contact of particulate polyethylene terephthalate with aphosphorus-containing organic solvent solution was carried out in thesame manner as in Example 466-1, except that acetone was used instead ofisopropanol. Then, the acetaldehyde content was measured in the samemanner as in Example 466-1. As a result, the acetaldehyde content was 40ppm.

Example 466-4

Contact of particulate polyethylene terephthalate with aphosphorus-containing organic solvent solution was carried out in thesame manner as in Example 466-1, except that hexane was used instead ofisopropanol. Then, the acetaldehyde content was measured in the samemanner as in Example 466-1. As a result, the acetaldehyde content was 35ppm.

Example 466-5

Contact of particulate polyethylene terephthalate with aphosphorus-containing organic solvent solution was carried out in thesame manner as in Example 466-1, except that 3.8 g (2% by weight interms of phosphorus atom based on isopropanol) of phosphoric acid wasused instead of 10.3 g of tributyl phosphate. Then, the acetaldehydecontent was measured in the same manner as in Example 466-1. As aresult, the acetaldehyde content was 36 ppm.

Example 466-1C

The same particulate polyethylene terephthalate as used in Example 466-1was dried at 70° C. for 16 hours, melted by heating at 285° C. for 10minutes and cooled to room temperature, without performing a contacttreatment with a phosphorus-containing organic solvent solution, to givea sample. Measurement of an acetaldehyde content in the sample resultedin 50 ppm.

Comparative Example 466-2

Contact of particulate polyethylene terephthalate with a phosphoric acidaqueous solution was carried out in the same manner as in Example 466-1,except that water was used instead of isopropanol and 3.8 g (2% byweight in terms of phosphorus atom based on water) of phosphoric acidwas used instead of 10.3 g of tributyl phosphate. Then, the acetaldehydecontent was measured in the same manner as in Example 466-1. As aresult, the acetaldehyde content was 45 ppm.

Example 462-1 Production of Polyester

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6458 parts by weight/hr) and ethyleneglycol (261 parts by weigh/hr) was continuously fed, and esterificationreaction was conducted under the condition of a temperature or 260° C.and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring.In the esterification reaction, the solid titanium compound prepared inExample 495-1 was fed at a rate of 0.187 part by weight/hr in terms oftitanium atom, and magnesium acetate was fed at a rate of 0.187 part byweight/hr in terms of magnesium atom. In the esterification reaction, amixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that the average residence time wascontrolled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Then, liquid phase polycondensation reaction of the low condensate wasconducted under the conditions of a temperature of 280° C. and apressure of 1 Torr, with feeding tributyl phosphate at a race of 0.831part by weight/hr.

The residence time (liquid phase polymerization time) required to attainan intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalatewas 95 minutes.

The polyethylene terephthalate obtained by the liquid phasepolymerization was crystallized at about 170° C. for 2 hours in anitrogen atmosphere and then filled in a tower type solid phasepolymerization reactor to perform solid phase polymerization at 210° C.for 14 hours in a nitrogen atmosphere.

In the resulting polyethylene terephthalate, the titanium atom contentwas 25 ppm, the magnesium atom content was 25 ppm, the titaniumatom/magnesium atom molar ratio was 0.5, the intrinsic viscosity was0.85 dl/g, the density was 1.40 g/cm³, and the acetaldehyde content was1.0 ppm.

In a stainless steel container, 2.5 kg of the polyethylene terephthalatewas immersed in 4 kg of a trimethyl phosphate aqueous solution of0.0695% by weight, and they were kept at room temperature for 4 hours.Thereafter, the particulate polyethylene terephthalate was separatedfrom the trimethyl phosphate aqueous solution, hydro-extracted and thendried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehydecontent in the resulting polyethylene terephthalate was 1.0 ppm. Usingthe polyethylene terephthalate, a stepped square plate molded productwas produced by the aforesaid method. The acetaldehyde content in thestepped square plate molded product was 9.0 ppm, and a difference in theacetaldehyde content between before and after the molding was 8.0 ppm.The intrinsic viscosity of the stepped square plate molded product was0.821 dl/g.

Example 462-2

In a stainless steel container, 2.5 kg of the same particulatepolyethylene terephthalate as used in Example 462-1 was immersed in 4 kgof a trimethyl phosphate aqueous solution of 0.0695% by weight. Then,the stainless steel container containing the polyethylene terephthalateand the trimethyl phosphate aqueous solution was externally heated tocontrol the internal temperature to 95° C. and kept for 4 hours toperform heat treatment. Thereafter, the particulate polyethyleneterephthalate was separated from the trimethyl phosphate aqueoussolution, hydro-extracted and then dried at 160° C. for 5 hours in astream of nitrogen. Using the resulting polyethylene terephthalate, astepped square plate molded product was produced by the aforesaidmethod. The acetaldehyde content in the stepped square plate moldedproduct was 9.5 ppm, and a difference in the acetaldehyde contentbetween before and after the molding was 8.5 ppm. The intrinsicviscosity of the stepped square plate molded product was 0.802 dl/g.

Example 462-1C

The same particulate polyethylene terephthalate as used in Example 462-1was molded into a stepped square plate molded product by the aforesaidmethod, without performing a contact treatment with aphosphorus-containing aqueous solution. The acetaldehyde content in thestepped square plate molded product was 20 ppm, and a difference in theacetaldehyde content between before and after the molding was 19 ppm.The intrinsic viscosity of the stepped square plate molded product was0.833 dl/g.

Comparative Example 462-2

Treatment of particulate polyethylene terephthalate was carried out inthe same manner as in Example 402-1, except that a phosphoric acidaqueous solution having the same concentration was used instead of thetrimethyl phosphate aqueous solution. Using the resulting polyethyleneterephthalate, a stepped square plate molded product was produced by theaforesaid method. The acetaldehyde content in the stepped square platemolded product was 13 ppm, and a difference in the acetaldehyde contentbetween before and after the molding was 12 ppm. The intrinsic viscosityof the stepped square plate molded product was 0.814 dl/g.

Example 462-3

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6329 parts by weight/hr), isophthalicacid (129 parts by weight) and ethylene glycol (2615 parts by weight/hr)was continuously fed, and esterification reaction was conducted underthe conditions of a temperature of 260° C. and a pressure of 0.9kg/cm²-G in a nitrogen atmosphere with stirring.

In the esterification reaction, a solid titanium compound prepared inthe same manner as in Example 462-1 was fed at a rate of 0.112 part byweight/hr in terms of titanium atom, and magnesium acetate was fed at arate of 0.187 part by weight/hr in terms of magnesium atom. In theesterification reaction, a mixture of water and ethylene glycol wasdistilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that the average residence time wascontrolled co 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Then, liquid phase polycondensation reaction of the low condensate wasconducted under the conditions of a temperature of 280° C. and apressure of 1 Torr, with feeding tributyl phosphate at a rate of 0.831part by weight/hr.

The residence time (liquid phase polymerization time) required to attainan intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalatewas 115 minutes.

The polyethylene terephthalate obtained by the liquid phasepolymerization was crystallized at about 170° C. for 2 hours in anitrogen atmosphere and then filled in a tower type solid phasepolymerization reactor to perform solid phase polymerization at 210° C.for 17 hours in a nitrogen atmosphere.

In the resulting polyethylene terephthalate, the titanium atom contentwas 15 ppm, the magnesium atom content was 25 ppm, the titaniumatom/magnesium atom molar ratio was 0.3, the intrinsic viscosity was0.83 dl/g, the density was 1.40 g/cm³, and the acetaldehyde content was0.9 ppm.

In a stainless steel container, 2.5 kg of the polyethylene terephthalatewas immersed in 4 kg of a trimethyl phosphate aqueous solution of0.0695% by weight, and they were kept at room temperature for 4 hours.Thereafter, the particulate polyethylene terephthalate was separatedfrom the trimethyl phosphate aqueous solution, hydro-extracted and thendried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehydecontent in the resulting polyethylene terephthalate was 0.8 ppm. Usingthe polyethylene terephthalate, a stepped square plate molded product asproduced by the aforesaid method. The acetaldehyde content in thestepped square plate molded product was 8.2 ppm, and a difference in theacetaldehyde content between before and after the molding was 7.4 ppm.The intrinsic viscosity of the stepped square plate molded product was0.819 dl/g.

Example 462-4

In a stainless steel container, the polyethylene terephthalate obtainedafter the solid phase polymerization in Example 462-3 was immersed inisopropanol at 95° C. and kept for 4 hours under heating.

Then, the polyethylene terephthalate was separated from isopropanol anddried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehydecontent in the resulting polyethylene terephthalate was 0.9 ppm. Usingthe polyethylene terephthalate, a stepped square plate molded productwas produced by the aforesaid method. The acetaldehyde content in thestepped square plate molded product was 9.5 ppm, and a difference in theacetaldehyde content between before and after the molding was 8.6 ppm.The intrinsic viscosity of the stepped square plate molded product was0.810 dl/g.

Example 462-5

In a stainless steel container, the polyethylene terephthalate obtainedafter the solid phase polymerization in Example 462-3 was immersed in anisopropanol solution of tributyl phosphate (tributyl phosphate: 0.0695%by weight) and kept for 2 hours under heating.

Then, the polyethylene terephthalate was separated from the isopropanolsolution and dried at 160° C. for 5 hours in a stream of nitrogen. Theacetaldehyde content in the resulting polyethylene terephthalate was 0.7ppm. Using the polyethylene terephthalate, a stepped square plate moldedproduct was produced by the aforesaid method. The acetaldehyde contentin the stepped square plate molded product was 8.2 ppm, and a differencein the acetaldehyde content between before and after the molding was 7.5ppm. The intrinsic viscosity of the stepped square plate molded productwas 0.808 dl/g.

Example 463-1 Production of Polyester

To a reactor in which 33500 parts by weigh of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6458 parts by weight/hr) and ethyleneglycol (2909 parts by weight/hr) was continuously fed, andesterification reaction was conducted under the conditions of atemperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogenatmosphere with stirring. In the esterification reaction, the solidtitanium compound prepared in Example 495-1 was fed at a rate of 0.187part by weight/hr in terms of titanium atom, and magnesium acetate wasfed at a rate of 0.187 part by weight/hr in terms of magnesium atom. Inthe esterification reaction, a mixture of water and ethylene glycol wasdistilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that the average residence time wascontrolled to 3.5 hours.

The number-average molecular weight of he low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Then, liquid phase polycondensation reaction or the low condensate wasconducted under the conditions of a temperature of 280° C. and apressure of 1 Torr, with Feeding tributyl phosphate at a rate of 0.831part by weight/hr.

The residence time (liquid chase polymerization time) required to attainan intrinsic viscosity (IV) of 0.55 dl/g of polyethylene terephthalatewas 87 minutes.

The polyethylene terephthalate obtained by the liquid phasepolymerization was crystallized at about 170° C. for 2 hours in anitrogen atmosphere and then filled in a tower type solid phasepolymerization reactor to perform solid phase polymerization at 210° C.for 25 hours in a nitrogen atmosphere.

In the resulting polyethylene terephthalate, the titanium atom contentwas 24 ppm, the magnesium atom content was 24 ppm, the titaniumatom/magnesium molar ratio was 0.5, the intrinsic viscosity was 0.760dl/g, the density was 1.40 g/cm³, and the cyclic trimer content was 0.3%by weight.

In a stainless steel container, 2.5 kg of the polyethylene terephthalatewas immersed in 4 kg of a trimethyl phosphate aqueous solution of0.0695% by weight, and they were kept at room temperature for 4 hours.Thereafter, the particulate polyethylene terephthalate was separatedfrom the trimethyl phosphate aqueous solution, hydro-extracted and thendried at 160° C. for 5 hours in a stream of nitrogen. The cyclic trimercontent in the resulting polyethylene terephthalate was 0.30% by weight(x % by weight). Using the polyethylene terephthalate, a stepped squareplate molded product was produced by the aforesaid method. The cyclictrimer content in the stepped square plate molded product was 0.35% byweight, a difference in the cyclic trimer content between before andafter the molding was 0.05% by weight (y % by weight), and the value of−0.2+0.2 was 0.14. The intrinsic viscosity of the stepped square platemolded product was 0.825 dl/g.

Example 463-2

In a stainless steel container, 2.5 kg of the same particulatepolyethylene terephthalate as used in Example 463-1 was immersed in 4 kgof a trimethyl phosphate aqueous solution of 0.0695% by weight. Then,the stainless steel container containing the polyethylene terephthalateand the trimethyl phosphate aqueous solution was externally heated tocontrol the internal temperature to 95° C. and kept for 4 hours atperform heat treatment. Thereafter, the particulate polyethyleneterephthalate was separated from the trimethyl phosphate aqueoussolution, hydro-extracted and then dried at 160° C. for 5 hours in astream of nitrogen. The cyclic trimer content in the resultingpolyethylene terephthalate was 0.30% by weight (x % by weight). Usingthe polyethylene terephthalate, a stepped square plate molded productwas produced by the aforesaid method. The cyclic trimer content in thestepped square plate molded product was 0.33% by weight (x % by weight),a difference in the cyclic trimer content between before and after themolding was 0.03% by weight (y % by weight), and the value of −0.20+0.2was 0.134. The intrinsic viscosity of the stepped square plate moldedproduct was 0.811 dl/g.

Example 463-1C

The same particulate polyethylene terephthalate as used in Example 463-1was molded into a stepped square plate molded product by the aforesaidmethod, without performing a constant treatment with aphosphorus-containing aqueous solution. The cyclic trimer content in thestepped square plate molded product was 0.52% by weight (x % by weight),a difference in the cyclic trimer content between before and after themolding was 0.22% by weight (y % by weight), and the value of −0.2+0.2was 0.096. The intrinsic viscosity of the stepped square plate moldedproduct was 0.833 dl/g.

Example 463-3

To a reactor in which 33500 parts by weight of a reaction solution wasresident during the steady operation, a slurry prepared by mixinghigh-purity terephthalic acid (6329 parts by weight/hr), isophthalicacid (129 parts by weight) and ethylene glycol (2615 parts by weight/hr)was continuously fed, and esterification reaction was conducted underthe conditions of a temperature of 260° C. and a pressure of 0.9kg/cm²-G in a nitrogen atmosphere with stirring. In the esterificationreaction, a solid titanium compound prepared in the same manner as inExample 463-1 was fed at a rate of 0.112 part by weight/hr in terms oftitanium atom, and magnesium acetate was fed at a rate of 0.187 part byweight/hr in terms of magnesium atom. In the esterification reaction, amixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuouslydrawn out of the system so that than average residence time wascontrolled to 3.5 hours.

The number-average molecular weight of the low condensate of ethyleneglycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

Then, liquid phase polycondensation reaction of the low condensate wasconducted under the conditions of a temperature of 280° C. and apressure of 1 Torr, with feeding tributyl phosphate at a rate of 0.831part by weight/hr.

The residence time (liquid phase polymerization time) required to attainan intrinsic viscosity (IV) of 058 dl/g of polyethylene terephthalatewas 100 minutes.

The polyethylene terephthalate obtained by the liquid phasepolymerization was crystallized at about 170° C. for 2 hours in anitrogen atmosphere and then filled in a tower type solid phasepolymerization reactor to perform solid phase polymerization at 210° C.for 22 hours in a nitrogen atmosphere.

In the resulting polyethylene terephthalate, the titanium atom contentwas 15 ppm, the magnesium atom content was 25 ppm, the titaniumatom/magnesium atom molar ratio was 0.3, the intrinsic viscosity was0.82 dl/g, the density was 1.40 g/cm³, and the cyclic trimer content was0.40% by weight.

In a stainless steel container, 2.5 kg of the polyethylene terephthalatewas immersed in 4 kg of a trimethyl phosphate aqueous solution of 00695%by weight, and they were kept at room temperature for 4 hours.Thereafter, the particulate polyethylene terephthalate was separatedfrom the trimethyl phosphate aqueous solution, hydro-extracted and thendried at 160° C. for 5 hours in a scream of nitrogen. The cyclic trimercontent in the resulting polyethylene terephthalate was 0.40% by weight(x % by weight). Using the polyethylene terephthalate, a stepped squareplate molded product was produced by the aforesaid method. The cyclictrimer content in the stepped square plate molded product was 0.48% byweight, a difference in the cyclic trimer content between before andafter the molding was 0.08% by weight (y % by weight), and the value of−0.2+0.2 was 0.104. The intrinsic viscosity of the stepped square platemolded product was 0.805 dl/g.

Example 463-4

In a stainless steel container, the polyethylene terephthalate obtainedafter the solid phase polymerization in Example 463-3 was immersed inisopropanol at 95° C. and kept for 4 hours under heating.

Then, the polyethylene terephthalate was separated from the isopropanoland dried at 160° C. for 5 hours in a stream of nitrogen. The cyclictrimer content in the resulting polyethylene terephthalate was 0.40% byweight (x % by weight). Using the polyethylene terephthalate, a steppedsquare plate molded product was produced by the aforesaid method. Thecyclic trimer content in the stepped square plate molded product was0.46% by weight, a difference in the cyclic trimer content betweenbefore and after the molding was 0.06% by weight (y % by weight), andthe value of −0.2+0.2 was 0.12. The intrinsic viscosity of the steppedsquare plate molded product was 0.810 dl/g.

Example 463-2C

The same particulate polyethylene terephthalate as used in Example 463-2was molded into a stepped square plate molded product by the aforesaidmethod, without performing a contact treatment with a trimethylphosphate aqueous solution. The cyclic trimer content in the steppedsquare plate molded product was 0.57% by weight (x % by weight), adifference in the cyclic trimer content between before and after themolding was 0.17% by weight (y % by weight), and the value of −0.2+0.2was 0.086. The intrinsic viscosity of the stepped square plate moldedproduct was 0.811 dl/g.

Example 469-1

To an esterification reactor, 76.81 mol of high-purity terephthalic acidand 86.03 mol of ethylene glycol were fed at 100° C. at atmosphericpressure, and 0.0045 mol of the titanium-containing solid compoundprepared in Example 495-1 was further added as a catalyst. Then, thetemperature of the reactor was raised to 260° C., and the reaction wasconducted for 340 minutes under a pressure of 1.7 kg/cm²-G in a nitrogenatmosphere. Water produced by the reaction was continually distilled offfrom the system.

Then, the total amount of the solution in the esterification reactor wastransferred into a polycondensation reactor beforehand set at 260° C. Tohe reactor, a solution of 0.0073 mol of tributyl phosphate in 6.44 molof ethylene glycol was further added at atmospheric pressure, and thetemperature of the reactor was raised to 280° C. from 260° C. over aperiod of 60 minutes, while the pressure was reduced to 2 Torr fromatmospheric pressure.

The reaction in the polycondensation reactor was further conducted for108 minutes, and the reaction product was drawn out of thepolycondensation reactor in the form of strands. The strands wereimmersed in water, cooled and cut into particles by a strand cutter toobtain polyethylene terephthalate. The polyethylene terephthalate has anintrinsic viscosity of 0.65 dl/g and a titanium content, as measured byatomic absorption analysis, of 28 ppm.

The polyethylene terephthalate obtained by the liquid phasepolymerization was then transferred into a solid phase polymerizationtower, crystallized at 170° C. for 2 hours in a nitrogen atmosphere, andthen subjected to solid phase polymerization at 210° C. for 13 hours toobtain particulate polyethylene terephthalate. The intrinsic viscosityof the polyethylene terephthalate was 0.825 dl/g. Using the polyethyleneterephthalate, a stepped square plate molded product was produced by theaforesaid method.

The haze of the part C of the stepped square molded product was 17.8%.Then, the polyethylene terephthalate was molded into a blow moldedarticle in the following manner.

A preform having a diameter of 28 mm was produced by an injectionmolding machine M-100A (manufactured by Meiki Seisakusho) under theconditions of a cylinder preset temperature of 260° C. and a moldtemperature of 10° C. In the molding, the injection molding temperaturewas 276° C. and the molding cycle was 54 seconds.

The preform was then subjected to stretch blow molding by the use of ablow molding machine (model No. LB01, manufactured by CORPOPLAST Co.)under the conditions of a stretch temperature of 110° C. and a blow moldtemperature of 30° C., to obtain a 1.5 liter blow molded article.

The appearance of the blow molded article was evaluated in the followingmanner.

Further, flowability (L/T) of the polyethylene terephthalate wasevaluated in the following manner using an injection molding machine ofM-70B model manufactured by Meiki Seisakusho. Moreover, an intrinsicviscosity of the resulting L/T specimen was measured. The results areset forth in Table 469-1.

In Examples 469-1 to 469-6 and Comparative Examples 469-1 to 469-4, eachproperty was evaluated in the following manner.

Intrinsic Viscosity (IV)

The intrinsic viscosity of the molded product was determined as follows.Using a mixed solvent of phenol and 1,1,2,2-tetrachloroethane (50/50 byweight), 10 a sample solution having a concentration of 0.5 g/dl wasprepared, and the solution viscosity was measured at 25° C. From thesolution viscosity, the intrinsic viscosity was calculated. Theintrinsic viscosity of the particulate polyethylene terephthalate wasdetermined as follows. 1.2 Grams of the polyethylene terephthalate wasdissolved in 15 cc of o-chlorophenol under heating, then cooled, and thesolution viscosity was measured at 25° C. From the solution viscosity,the intrinsic viscosity was calculated.

Haze

In a tray dryer, 2 kg of particulate polyethylene terephthalate as astarting material was dried at 140° C. under a pressure of 10 Torr for 1hours or more, to allow the particulate polyethylene terephthalate tohave a water content of not more than 50 ppm.

Then, the dried particulate polyethylene terephthalate was injectionmolded by a M-70A injection molding machine manufactured by MeikiSeisakusho K.K. under the conditions of a cylinder temperature of 275°C. and a mold cooling water temperature of 15° C., to produce a steppedsquare plate molded product.

In detail, the stepped square plate molded product was produced byfeeding the dried particulate polyethylene terephthalate to an injectionmolding machine adjusted to have molding conditions of metering of 12seconds and injection of 60 seconds through a hopper. The residence timeof the molter, resin in the molding machine was about 72 seconds. Theweight of the resin used per stepped square plate molded product was 75g. As a specimen for measuring a haze, any one of the eleventh tofifteenth stepped square molded products from the beginning of theinjection molding was adopted.

The stepped square plate molded product has a shape shown in FIG. 1, andthe thicknesses of the parts A, B and C are about 6.5 mm, about 5 mm andabout 4 mm, respectively. In the present invention, the haze of the partC of the stepped square plate molded product was measured using a hazemeter (Suga tester) HGM-2DP.

Appearance of Blow Molded Article

A haze value (irregular reflectance of white light) at the almostcentral portion of a sidewall of the hollow container was measured.Based on the haze value (%), appearance of the blow molded article wasevaluated as follows.

-   -   AA: 0≦haze value<5    -   BB: 5≦haze value        Flowability (L/T) Measuring Method

The flowability was measured by the method described in thespecification.

Examples 469-2 to 469-5

Polyethylene terephthalate was produced in the same manner as in Example469-1, except that the polycondensation catalyst and the polymerizationconditions were changed as shown in Table 409-1.

Using the polyethylene terephthalate, a blow molded article was producedin the same manner as in Example 469-1, and appearance thereof wasevaluated. Further, flowability (L/T) and an intrinsic viscosity of theL/T specimen were measured in the same manner as in Example 469-1. Theresults are set forth in Table 469-1.

Comparative Example 469-1

Polyethylene terephthalate (intrinsic viscosity: 0.825 dl/g; type of acatalyst determined by atomic absorption analysis: antimony compound;and the antimony content: 235 ppm) was used.

Using the polyethylene terephthalate, a blow molded article was producedin the same manner as in Example 469-1, and appearance thereof wasevaluated. Further, flowability (L/T) and an intrinsic viscosity of theL/T specimen were measured In the same manner as in Example 469-1. Theresults are set forth in Table 469-1.

Comparative Example 469-2

Polyethylene terephthalate (intrinsic viscosity: 0.843 dl/g; the type ofa catalyst determined by atomic absorption analysis: antimony compound;and the antimony content: 232 ppm) was used.

Using the polyethylene terephthalate, a blow molded article was producedin the same manner as in Example 469-1, the appearance thereof wasevaluated. Further, flowability (L/T) and an intrinsic viscosity of theL/T specimen were measured in the same manner as in Example 469-1. Theresult are set forth in Table 469-1.

Comparative Example 469-3

Polyethylene terephthalate (intrinsic viscosity: 0.778 dl/g; the type ofa catalyst determined by atomic absorption analysis: germanium compound;and the germanium content: 56 ppm.) was used.

Using the polyethylene terephthalate, a blow molded article was producedin the same manner as in Example 469-1, and appearance thereof wasevaluated. Further, flowability (L/T) and an intrinsic viscosity of theL/T specimen were measured in the same manner as in Example 469-1. Theresults are set forth in Table 469-1.

Comparative Example 469-4

Polyethylene terephthalate (intrinsic viscosity: 0.823 dl/g; type ofcatalyst determined by atomic absorption analysis; germanium compound;and the germanium content: 42 ppm) was used.

Using the polyethylene terephthalate, a blow molded article was producedin the same manner as in Example 469-1, and appearance thereof wasevaluated. Further, flowability (L/T) and an intrinsic viscosity of theL/T specimen were measured in the same manner as in Example 469-1. Theresults are set forth in Table 469-1.

Example 469-6 Preparation of Titanium-containing Solid Compound

Deionized water of 500 ml was weighed out and introduced into a 1000 mlglass beaker. To the deionized water, 0.15 g of anhydrous magnesiumhydroxide was added to give a dispersion. The dispersion in the beakerwas cooled in an ice bath, and thereto was dropwise added 5 g oftitanium tetrachloride with stirring. The liquid became acidic, and themagnesium hydroxide was dissolved. When production of hydrogen chloridestopped, the beaker containing the reaction solution was taken out ofthe ice bath, and 25% aqueous ammonia was dropwise added with stirring,to adjust pH of the solution to 8. The precipitate oftitanium-containing complex hydroxide produced was separated from thesupernatant liquid by centrifugation of 2500 revolutions for 15 minutes.Then, the precipitate of titanium-containing complex hydroxide waswashed five times with deionized water. After the washing, solid-liquidseparation was carried out by centrifugation of 2500 revolutions for 15minutes. The washed titanium-containing complex hydroxide was vacuumdried at 70°0 C. under a pressure of 10 Torr for 18 hours to removewater content, whereby a titanium-containing solid compound wasobtained.

In the titanium-containing solid compound, the ratio between titaniumatom and magnesium atom was 91:9 by mol. Prior to use as apolycondensation catalyst, the titanium-containing solid compound waspulverized into particles of about 10μ.

Polycondensation reaction, granulation and solid polymerization reactionwere carried out in the same manner as in Example 469-1, except that thetitanium-containing solid compound prepared above was used as thepolycondensation catalyst. Using the resulting polyethyleneterephthalate, a blow molded article was produced in the same manner asin Example 469-1, and appearance thereto was evaluated. Further,flowability (L/T) and an intrinsic viscosity of the L/T specimen weremeasured in the same manner as in Example 469-1. The results are setforth in Table 469-1.

As shown in Table 409-1, the polyethylene terephthalate according to theinvention has higher flowability than conventional polyethyleneterephthalate, and therefore the polyethylene terephthalate of theinvention is excellent in moldability. The blow molded article obtainedfrom the polyethylene terephthalate of the invention has excellentappearance similarly to the blow molded article obtained from theconventional polyethylene terephthalate.

TABLE 469-1 Polycondensation catalyst (I) Co-catalyst compound (II)Intrinsic Amount Amount viscosity added *3 Residue added *3 ResidueIntrinsic Flow- of L/T (% by *4 (% by *4 viscosity Haze ability specimenType mol) (ppm) Type mol) (ppm) (dl/g) (%) L/T (dl/g) Appearance Ex.469-1 *1 0.013 28 — — — 0.825 17.8 275 0.761 AA Ex. 469-2 *1 0.013 27Mg(OAc)₂ 0.020 22 0.803 1.5 277 0.749 AA Ex. 469-3 *1 0.013 13 Mg(OAc)₂0.020 25 0.813 2.4 267 0.767 AA Ex. 469-4 *1 0.013 25 Mg(OAc)₂ 0.010 160.820 13.7 272 0.763 AA Ex. 469-5 *1 0.013 29 Zn(OAc)₂ 0.020 59 0.80713.7 267 0.769 AA Ex. 469-6 *2 Ti: 0.013 Ti: 27 — — — 0.815 7.2 2760.769 AA Mg: 0.001 Mg: 4 Comp. Ex. Sb — 235 — — — 0.825 3.5 263 0.760 AA469-1 Comp. Ex. Sb — 232 — — — 0.843 2.7 259 0.772 AA 469-2 Comp. Ex. Ge— 56 — — — 0.778 6.3 271 0.745 AA 469-3 Comp. Ex. Ge — 42 — — — 0.8232.1 256 0.774 AA 469-4 *1: titanium-containing solid compound preparedin Example 495-3 *2: solid titanium compound prepared in Example 496-6*3: in terms of metal atom based on terephthalic acid unit *4: contentof metal atom based on particulate polyethylene terephthalate Mg(OAc)₂:magnesium acetate Zn(OAc)₂: zinc acetate

1. A catalyst for polyester production, comprising a solid titaniumcompound (I-a) which is obtained by dehydro-drying a hydrolyzateobtained by hydrolyzing a titanium halide and has a molar ratio (OH/Ti)of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than4.
 2. A catalyst for polyester production, comprising atitanium-containing solid compound (I-b) which is obtained bydehydro-drying a hydrolyzate obtained by hydrolyzing a mixture of atitanium halide and a compound of at least one element selected fromelements other than titanium or a precursor of the compound and has amolar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding0.09 and less than
 4. 3. The catalyst for polyester production asclaimed in claim 2, wherein the compound of at least one elementselected from elements other than titanium or the precursor of thecompound is a compound of at least one element selected from the groupconsisting of beryllium, magnesium, calcium, strontium, barium,scandium, yttrium, lanthanium, zirconium, hafnium, vanadium, niobium,tantalum, chromium, molybdenum, tungsten, manganese, iron, ruthenium,cobalt, rhodium, nickel, palladium, cooper, zinc, boron, aluminum,gallium, silicon, germanium, tin, antimony and phosphorus or a precursorof the compound.
 4. A catalyst for polyester production comprising: apolycondensation catalyst component comprising the solid titaniumcompound (I-a) of claim 1 or the titanium-containing solid compound(I-b) of claim 2, and (II) a co-catalyst component comprising a compoundof at least one element selected from the group consisting of beryllium,magnesium, calcium, strontium, barium boron, aluminum, gallium,manganese, cobalt, zinc, germanium, antimony and phosphorus.
 5. Acatalyst for polyester production, comprising a solid titanium compound(I-f) obtained by a process comprising bringing a titanium halide intocontact with water to hydrolyze the titanium halide and thereby obtainan acid solution containing a hydrolyzate of the titanium halide,adjusting pH of the solution to 2 to 6 by the use of a base, anddehydro-drying the resulting precipitate.
 6. A catalyst for polyesterproduction, comprising a solid titanium compound (I-i) which is obtainedby dehydro-drying titanium hydroxide and has a crystallinity, ascalculated from an X-ray diffraction pattern having 2θ (diffractionangle) of 18° to 35°, of not more than 50%.
 7. A catalyst for polyesterproduction, comprising: (I) a polycondensation catalyst componentcomprising the solid titanium compound (I-i) of claim 6, and (II) aco-catalyst component comprising a compound of at least one elementselected from the group consisting of beryllium, magnesium, calcium,strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc,germanium, antimony and phosphorus.
 8. A catalyst for polyesterproduction, comprising a slurry obtained by heating a mixture of: (A-1)a hydrolyzate (I-j) obtained by hydrolyzing a titanium compound or ahydrolyzate (I-k) obtained by hydrolyzing a mixture of a titaniumcompound and a compound of at least one element selected from elementsother than titanium or a precursor of the compound, (B) a basiccompound, and (C) an aliphatic diol.
 9. The catalyst for polyesterproduction as claimed in claim 8, wherein the basic compound (B) is atleast one compound selected from tetraethylammonium hydroxide,tetraethylammonium hydroxide, aqueous ammonia, sodium hydroxide,potassium hydroxide, N-ethylmorpholine and N-methylmorpholine.
 10. Thecatalyst for polyester production as claimed in claim 8 or 9, whereinthe aliphatic diol (C) is ethylene glycol.
 11. A catalyst for polyesterproduction, comprising: (A-2) a hydrolyzate (I-m) obtained byhydrolyzing a titanium halide or a hydrolyzate (I-n) obtained byhydrolyzing a mixture of a titanium halide and a compound of at leastone element selected from elements other than titanium or a precursor ofthe compound, and (D) a metallic phosphate containing at least oneelement selected from beryllium, magnesium, calcium, strontium, boron,aluminum, gallium, manganese, cobalt and zinc.
 12. The catalyst forpolyester production as claimed in claim 11, wherein the metallicphosphate (D) is magnesium hydrogenphosphate or trimagnesiumdiphosphate.
 13. A catalyst for polyester production, comprising aslurry obtained by heating a mixture of: (A-2) a hydrolyzate (I-m)obtained by hydrolyzing a titanium halide or a hydrolyzate (I-n)obtained by hydrolyzing a mixture of a titanium halide and a componentof at least one element selected from elements other than titanium or aprecursor of the compound, (E) a metallic compound containing at leastone element elected from beryllium, magnesium, calcium, strontium,boron, aluminum, gallium, manganese, cobalt and zinc, (F) at least onephosphors compound selected from phosphoric acid and phosphoric esters,and (G) an aliphatic diol.
 14. The catalyst for polyester production asclaimed in claim 13, wherein the metallic compound (E) is a magnesiumcompound, the phosphatic compound (F) is phosphoric acid or trimethylphosphate, and the aliphatic diol (G) is ethylene glycol.
 15. Thecatalyst for polyester production as claimed in claim 13 or 14, whereinthe heating temperature of the mixture or the components (A-2), (E), (F)and (G) is in the range of 100 and 200° C., and the heating time is inthe range of 3 minutes to 5 hours.
 16. A process for producing apolyester comprising polycondensing an aromatic dicarboxylic acid or anester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof in the presence of the catalyst asclaimed in any one of claims 1, 2, 5, 6, 8, 11,
 13. 17. A process forproducing a polyester, comprising an esterification step in which anaromatic dicarboxylic acid or an ester-forming derivative thereof and analiphatic diol an ester-forming derivative thereof are esterified toform a low condensate and a polycondensation step in which the lowcondensate is polycondensed in the presence of a polycondensationcatalyst to increase the molecular weight, wherein: the polycondensationcatalyst used is a catalyst comprising: (I) a polycondensation catalystcomponent comprising a hydrolyzate (I-j) obtained by hydrolyzing atitanium compound or a hydrolyzate (I-k) obtained by hydrolyzing amixture of a titanium compound and a compound of at least one elementselected from elements other than titanium or a precursor of thecompound, and (II) a co-catalyst component comprising a compound of atleast one element selected from the group consisting of beryllium,magnesium, calcium, strontium, barium, boron, aluminum, gallium,manganese, cobalt, zinc, germanium, antimony and phosphorus; and thepolycondensation catalyst component (I) is added to the esterificationreactor before the beginning of the esterification reaction orimmediately after the beginning of the esterification reaction.
 18. Theprocess for producing a polyester as claimed in claim 17, wherein theco-catalyst component (II) is a magnesium compound.
 19. A process forproducing a polyester, comprising polycondensation an aromaticdicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative thereof in the presence ofa polycondensation catalyst selected from the following catalysts (1) to(3) and a phosphoric ester to produce a polyester; (1) apolycondensation catalyst comprising a hydrolyzate (I-m) obtained byhydrolyzing a titanium halide, (2) a polycondensation catalystcomprising a hydrolyzate (I-n) obtained by hydrolyzing a mixture of atitanium halide and a compound of at least one element selected fromelements other than titanium or a precursor of the compound, and (3) apolycondensation catalyst comprising: the hydrolyzate (I-m) or (I-n),and a compound of at least one element selected from the groupconsisting of beryllium, magnesium, calcium, strontium, barium, boron,aluminum, gallium, manganese, cobalt, zinc, germanium and antimony, aphosphate or a phosphite.
 20. The process for producing a polyester asclaimed in claim 19, wherein the phosphoric ester is tributyl phosphate,trioctyl phosphate or triphenyl phosphate.
 21. A process for producing apolyester, comprising polycondensing an aromatic dicarboxylic acid or anester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof in the presence of a polycondensationcatalyst selected from the following catalyst (1) to (3) and at leastone compound selected from cyclic lactone compounds and hindered phenolcompounds to produce a polyester; (1) a polycondensation catalystcomprising a hydrolyzate (I-m) obtained by hydrolyzing a titaniumhalide, (2) a polycondensation catalyst comprising a hydrolyzate (I-n)obtained by hydrolyzing a mixture of a titanium halide and a compound ofat least one element selected from elements other than titanium or aprecursor of the compound, and (3) a polycondensation catalystcomprising: the hydrolyzate (I-m) or (I-n), and a compound of at leastone element selected from the group consisting of beryllium, magnesium,calcium, strontium,, barium, boron, aluminum, gallium, manganese,cobalt, zinc, germanium and antimony, a phosphate or a phosphite. 22.The process for producing a polyester as claimed in claim 21, wherein atleast one phosphorus compound selected from phosphoric acid andphosphoric esters is further used in combination.
 23. The process forproducing a polyester as claimed in claim 21 or 22, wherein the at leastone compound selected from cyclic lactone compounds and hindered phenolcompounds is a mixture of5,7-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one,tetrakis(methylene-3(3,5-di-t-butyl-4-hyroxyphenyl)propionate)methaneand tris(2,4-di-t-butylphenyl)phosphite.
 24. A process for producing apolyester, comprising an esterification step in which an aromaticdicarboxylic acid or an ester-forming derivative thereof and analiphatic diol or an ester-forming derivative thereof are esterified toform a low condensate and a polycondensation step in which the lowcondensate is polycondensed in the presence of a polycondensationcatalyst to increase the molecular weight, wherein: the polycondensationcatalyst used is a catalyst comprising: (I) a polycondensation catalystcomponent comprising a hydrolyzate (I-m) obtained by hydrolyzing atitanium halide or a hydrolyzate (I-n) obtained by hydrolyzing a mixtureof a titanium halide and a compound of at least one element selectedfrom elements other than titanium or a precursor of the compound, and(II) a co-catalyst component comprising a compound of at least oneelement selected from the group consisting of beryllium, magnesium,calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt,zinc, germanium, antimony and phosphorus; and a tint adjusting agent isadded in the esterification step or the polycondensation step.
 25. Theprocess for producing a polyester as claimed in claim 24, wherein thetint adjusting agent is at least one agent selected from Solvent Blue104, Pigment Red 263, Solvent Red 135, Pigment Blue 29, Pigment Blue15:1, Pigment Blue 15:3, Pigment Red 187 and Pigment Violet
 19. 26. Theprocess for producing a polyester as claimed in claim 24 or 25, whereinthe co-catalyst component (II) is a magnesium compound.
 27. A method fortreating a polyester, comprising bringing a polyester, which is obtainedby the use of titanium compound catalyst and in which the reaction hasbeen completed, into contact with a phosphorus acid aqueous solution, aphosphoric ester aqueous solution, a phosphorous ester aqueous solutionor a hypophosphorous ester aqueous solution, each of said solutionhaving a concentration of not less than 10 ppm in terms of phosphorusatom.
 28. The method for treating a polyester as claimed in claim 27,wherein the polyester has an intrinsic viscosity of not less than 0.50dl/g, a density of not less than 1.37 g/cm³ and an acetaldehyde contentof not more than 5 ppm.
 29. The method for treating a polyester asclaimed in claim 27 or 28, wherein polyethylene terephthalate, which isobtained by the use of a titanium compound catalyst and in which thereaction has been completed, is treated.
 30. A method for treating apolyester, comprising bringing a polyester, which is obtained by the useof a titanium compound catalyst and in which the reaction has beencompleted, into contact with an organic solvent.
 31. The method fortreating a polyester as claimed in claim 30, wherein the polyester hasan intrinsic viscosity of not less than 0.50 dl/g, a density of not lessthan 1.37 g/cm³ and an acetaldehyde content of not more than 5 ppm. 32.The method for treating a polyester as claimed in claim 30 or 31,wherein the organic solvent is a solvent selected from alcohols,saturated hydrocarbons and ketones.
 33. The method for treating apolyester as claimed in any one of claims 30 to 31, wherein the organicsolvent is isopropanol or acetone.
 34. The method of treating apolyester as claimed in any one of claims 30 to 31, wherein polyethyleneterephthalate, which is obtained by the use of a titanium compoundcatalyst and in which the reaction has been completed, is treated.
 35. Amethod for treating a polyester, comprising bringing polyester, which isobtained by the use of a titanium compound catalyst and in which thereaction has been completed, into contact with an organic solventsolution of phosphoric acid, an organic solvent solution of phosphoricester, an organic solvent solution of phosphorous acid, an organicsolvent solution of hypophosphorous acid, an organic solvent solution ofa phosphorous ester or an organic solvent solution of a hypophosphorousester, each of said solutions having a concentration of not less than 10ppm in terms of phosphorus atom.
 36. The method for treating a polyesteras claimed in claim 35, wherein the polyester has an intrinsic viscosityof not less than 0.50 dl/g, a density of not less than 1.37 g/cm³ and anacetaldehyde content of not more than 5 ppm.
 37. The method for treatinga polyester as claimed in claim 35 or 36, wherein the phosphoric esteris tributyl phosphate, triphenyl phosphate or trimethyl phosphate. 38.The method for treating a polyester as claimed in claim 35, wherein theorganic solvent is selected from alcohols, saturated hydrocarbons andketones.
 39. The method for treating a polyester as claimed in claim 35,wherein the organic solvent is isopropanol or acetone.
 40. The methodfor treating a polyester as claimed in claim 35, wherein polyethyleneterephthalate, which is obtained by the use of a titanium compoundcatalyst and in which the reaction has been completed, is treated.
 41. Apolyester (P-1) obtained by polycondensing an aromatic dicarboxylic acidor an ester-forming derivative thereof and an aliphatic diol or anester-forming derivative thereof in the presence of a catalyst forpolyester production comprising: a polycondensation catalyst componentcomprising a solid titanium compound (I-c) obtained by dehydro-drying ahydrolyzate obtained by hydrolyzing a titanium halide, and (II) aco-catalyst comprising a compound of at least one element selected fromthe group consisting of beryllium, magnesium, calcium, strontium,barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium,antimony and phosphorus, wherein the titanium content is in the range 1to 100 ppm, the magnesium content is in the range of 1 to 200 ppm, andthe weight ratio (Mg/Ti) of magnesium to titanium is not less than 0.01.42. The polyester (P-1) as claimed in claim 41, which is polyethyleneterephthalate.
 43. A polyester (P-2) having the following properties: atitanium atom is contained in an amount of 0.1 to 200 ppm, a metal atomM selected from beryllium, magnesium, calcium, strontium, barium, boron,aluminum, gallium, manganese, cobalt, zinc and antimony is contained inan amount of 0.1 to 500 ppm, the molar ratio (titanium atom/metal atomM) of the titanium atom to the metal atom M is in the range of 1/50 to50/1, and a tint adjusting agent is contained in an amount of 0.01 to100 ppm.
 44. A polyester (P-3) having the following properties: theintrinsic viscosity is not less than 0.50 dl/g, a titanium atom iscontained in an amount of 0.1 to 200 ppm, a metal atom M selected fromberyllium, magnesium, calcium, strontium, barium, boron, aluminum,gallium, manganese, cobalt, zinc and antimony is contained in an amountof 0.1 to 500 ppm, the molar ratio (titanium atom/metal atom M) of thetitanium atom to the metal atom M is in the range of 0.05 to 50, and thecontent of acetaldehyde is not more than 4 ppm, and when thisacetaldehyde content is taken as W₀ ppm and a content of acetaldehyde ina stepped square plate molded product obtained by heating said polyesterto a temperature of 275° C. to melt it and molding the molten polyesteris taken as W₁ ppm, the value of W₁−W₀ is not more than 10 ppm.
 45. Thepolyester (P-3) as claimed in claim 44, wherein the titanium atom isderived from a polycondensation catalyst obtained by hydrolysis of atitanium halide.
 46. The polyester (P-3) as claimed in claim 44 or 45,which is polyethylene terephthalate.
 47. A polyester (P-4) having thefollowing properties: the intrinsic viscosity is not less than 0.50dl/g, a titanium atom is contained in an amount of 0.1 to 200 ppm, ametal atom M selected from beryllium, magnesium, calcium, strontium,barium, boron, aluminum, gallium, manganese, cobalt, zinc and antimonyis contained in an amount of 0.1 to 500 ppm, the molar ratio (titaniumatom/metal atom M) of the titanium atom to the metal atom M is in therange of 0.05 to 50, and the content of a cyclic trimer is not more than0.5% by weight, and when this cyclic trimer content is taken as x % byweight and a content of a an increase in cyclic trimer in a steppedsquare plate molded product obtained by heating said polyester to atemperature of 290° C. to melt it and molding the molten polyester istaken as y % by weight, x and y satisfy the following relationy≦−0.2x−0.2 y≦−0.2x+0.2.
 48. The polyester (P-4) as claimed in claim 47,wherein the titanium atom is derived from a polycondensation catalystobtained by hydrolysis of at titanium halide.
 49. The polyester (P-4) asclaimed in claim 47 or 48, which is polyethylene terephthalate.
 50. Amolded product obtained from the polyester (P-1) as claimed in any oneof the claims 41 or
 42. 51. The molded product as claimed in claim 50,which is a blow molded article.
 52. The molded product as claimed inclaim 50, which is a film or a sheet.
 53. The molded product as claimedin claim 50, which is a fiber.
 54. A blow molded article obtained fromthe polyester (P-4) as claimed in any of claims 47 or 48 and having acyclic trimer content of not more than 0.6% by weight.
 55. A perform fora blow molded article which is obtained from a polyester (P-5) havingthe following properties: when the ratio (L/T) of a flow length (L) to aflow thickness (T) in the injection molding of said polyester at 290° C.is taken as Y and the intrinsic viscosity of a molded product obtainedby the injection molding is taken as X(dl/g), X and Y satisfy thefollowing relationY≧647−500X.
 56. A blow molded article obtained from the perform of claim55.